Archive for the ‘Security’ Category

Windows Server 2008 provides several tools that can be used when troubleshooting Kerberos Authentication

 

Klist.exe: Kerberos List: This tool is installed on Windows Server 2008 domain controllers and is available for download as part of the Windows Server 2003 Resource Kit tools.

 

Kerberos List is a command-line tool that is used to view and delete Kerberos tickets granted to the current logon session. To use Kerberos List to view tickets, you must run the tool on a computer that is a member of a Kerberos realm.

 

Kerbtray.exe: Kerberos Tray: Kerberos Tray is available for download as part of the Windows Server 2003 Resource Kit tools.

 

Kerberos Tray is a graphical user interface tool that displays ticket information for a computer running Microsoft’s implementation of the Kerberos version 5 authentication protocols. You can view and purge the ticket cache by using the Kerberos Tray tool icon located in the notification area of the desktop. By positioning the cursor over the icon, you can view the time left until the initial TGT expires. The icon also changes in the hour before the Local Security Authority (LSA) renews the ticket.

 

Tokensz.exe: Kerberos Token Size: Kerberos Token Size is available for download from the Microsoft download center.

 

You can use Kerberos Token Size to verify if the source of the Kerberos errors stems from a maximum token size issue. The tool will simulate an authentication request and report the size of the resulting Kerberos token. The tool will also report the maximum supported size for the token.

 

Setspn.exe: The Setspn utility is installed on Windows Server 2008 domain controllers and is included in the Windows Server 2003 Support Tools.

 

The Setspn utility allows you to read, modify, and delete the Service Principal Names (SPN) directory property for an Active Directory service account. Because SPNs are security-sensitive, you can only set SPNs for service accounts if you have domain administrator privileges.

 

Ksetup.exe: The Ksetup utility is installed on Windows Server 2008 domain controllers and is included in the Windows Server 2003 Support Tools.

 

The Ksetup utility configures a client connected to a server running Windows Server 2008 to use a server running Kerberos V5. The client then uses a Kerberos V5 realm instead of a Windows Server 2008 domain.

 

Ktpass.exe: The Ktpass utility is installed on Windows Server 2008 domain controllers and is included in the Windows Server 2003 Support Tools.

 

The Ktpass utility is used to configure a non–Windows Server Kerberos service as a security principal in the Windows Server 2008 AD DS.

 

W32tm.exe: Windows Time: This tool is included in Microsoft Windows server and client operating systems.

 

W32tm.exe is used to configure Windows Time service settings. It can also be used to diagnose problems with the time service.


If you have evaluated EFS in Windows 2000 and found critical features missing, it’s worth taking a second look at EFS in Windows Server 2003 and XP. The changes include the following:

  • New and more cryptographically robust encryption methods. You can now choose between DESX encryption (used by Windows 2000) and 3DES (Triple-DES), an algorithm that complies with government standards for handling of non-classified documents.
  • Offline file encryption. This feature is one of the most significant improvements in Windows Server 2003 and XP. It enables users to use a highly convenient feature, offline file storage, while retaining the ability to protect their files with encryption.
  • Encrypted file transfer over WebDAV. The Web-based Distributed Authorizing and Versioning redirector uses HTTP rather than SMB. Encrypted files are transferred in their encrypted state rather than being decrypted prior to transport as happens with SMB. Also, servers can store encrypted files using WebDAV without compromising security with Kerberos delegations.
  • More flexible group policy control. EFS can now be disabled throughout a domain with a single click of the mouse in a group policy. This contrasts with Windows 2000, which requires removing and re-importing X.509 certificates to control encryption.
  • Shared encrypted files. Users with encrypted files can assign access to other users. This enhances the use of EFS in a workgroup. Only individual users can be given access, not groups. Additional users can only be selected by users who already have access.
  • Copy warnings. Explorer now warns users when they attempt to copy or move encrypted files to an unprotected location such as a Zip drive, floppy drive, or FAT partition. New switches in COPY and XCOPY permit overriding these protections, if necessary.
  • Visual cues. The Explorer shell now shows the names of encrypted files and folders in a different color, similar to the way compressed files are displayed in Windows 2000.
  • Improved command-line administration. The CIPHER command-line utility has been updated with several new features, including the ability to generate file recovery certificates, the ability to search for encrypted files on a volume, the ability to refresh certificates for all encrypted files on a volume, and the ability to wipe all unused disk space to remove temporary files. (The wipe feature was released in Windows 2000 SP3.)
  • Security improvements. Although not strictly an EFS improvement, the handling of the crypto Master key has been changed so that it is not updated when a local user password is changed by anyone other than the user. This eliminates a serious deficiency for standalone laptops and desktops. Now a hacker cannot use utilities to change a user’s password (or the Administrator password) on a standalone machine to gain access to encrypted files.

Not every change is a welcome one, however. In Windows 2000, files cannot be encrypted without the certificate of a Data Recovery Agent (DRA). This ensures that a user cannot encrypt files and then quit the company and leave you without a means of recovering the files. In Windows Server 2003 and XP, it is possible to encrypt files without a DRA. This “feature” has potentially serious consequences because users could encrypt their files and then lose the private key, thereby losing access to the files permanently.

Problem

You want to ensure that users can only authenticate to Active Directory using strong authentication protocols.

Solution

Using a graphical user interface
  1. Open the Group Policy Management Console snap-in.

  2. In the left pane, expand the Forest container, expand the Domains container, browse to the domain you want to administer, and expand the Group Policy Objects container.

  3. Right-click on the GPO that controls the configuration of your domain controllers and select Edit. (By default, this is the Default Domain Controller Policy, but it may be a different GPO in your environment.) This will bring up the Group Policy Object Editor.

  4. Browse to Computer Configuration Windows Settings Security Settings Local Policies Security Options.

  5. Double-click on “Network security: LAN Manager Authentication Level.” Place a check mark next to “Define this policy setting.”

  6. Select “Send NTLMv2 responses only/refuse LM & NTLM.” Click OK.

  7. Wait for Group Policy to refresh, or type gpupdate /force from the command prompt of a Windows Server 2003 domain controller. On a Windows 2000 DC, use the secedit command with the /refreshpolicy switch.

Discussion

Microsoft operating systems have supported different flavors of LAN Manager (LM) and NT LAN Manager (NTLM) authentication since the earliest days of Windows. LM authentication is an extremely old and weak authentication protocol that should no longer be used in production environments unless absolutely necessary. By default, Windows 2000 Active Directory supported client authentication attempts using LM, NTLM, or NTLMv2; Windows Server 2003 supports only NTLM and NTLMv2 out of the box.

The strongest NTLM authentication scheme you can select is to refuse LM and NTLM authentication from any client, and to only respond to clients using NTLMv2. Depending on your client configuration, though, enabling this option may require changes on the client side as well. You can apply the same setting to a GPO linked to your Active Directory domain to ensure that all of your clients will use NTLMv2 instead of older, weaker protocols.


Problem

You want to enable or disable anonymous access to the information stored in the Active Directory database.

Solution

Using a graphical user interface

  1. Open the Active Directory Users and Computers (ADUC) snap-in.
  2. If you need to change domains, right-click on Active Directory Users and Computers in the left pane, select “Connect to Domain,” enter the domain name, and click OK.
  3. Navigate to the Builtin container. Double-click on the Pre-Windows 2000 Compatible Access group.
  4. Click the Members tab.
  5. Select the Everyone group and click the Remove button. Click Yes and then OK to confirm.
  6. Select the Anonymous Logon user and click the Remove button. Click Yes and then OK to confirm.
  7. If the Authenticated Users group is not present in the group membership list, click Add to include it and then click OK.

Using a command-line interface

You have three command-line choices to modify the Pre-Windows 2000 Access security group: net localgroup, DSMod, or AdMod. net localgroup takes the following syntax:

> net localgroup ”

Pre-Windows 2000 Compatible Access” Everyone /delete

> net localgroup “Pre-Windows 2000 Compatible Access” “Anonymous Logon” /delete

> net localgroup “Pre-Windows 2000 Compatible Access” “Authenticated Users” /add

To update the group membership using DSMod so that it only includes Authenticated Users, enter the following:

> dsmod group “cn=Pre-Windows 2000 Compatible Access,cn=Builtin,

<DomainDN>” -chmbr “cn=S-1-5-11,cn=ForeignSecurityPrincipals,<DomainDN>”

To use AdMod, use the following syntax:

> admod b “cn=Pre-Windows 2000 Compatible Access,cn=Builtin,

<DomainDN>” member::”cn=S-1-5-11,cn=ForeignSecurityPrincipals,<DomainDN>”

Discussion

Anonymous access to Active Directory is controlled by membership in the Pre-Windows 2000 Compatible Access security group, located in the cn=Builtin container. This group is named like that because some legacy applications and operating systems, most notably Windows NT 4.0 RAS servers, required anonymous access to the information stored in AD in order to function properly. The default membership of this group depends on whether you selected “Permissions compatible with pre-Windows 2000 operating systems” or “Permissions compatible with only Windows 2000 and Windows 2003” when you ran dcpromo. If you selected the former, the Everyone group and the Anonymous Logon SID were added to Pre-Windows 2000 Compatible Access; if the latter, only Authenticated Users was added.

In the DSMod, AdMod, and VBScript solutions, the Authenticated Users group was specified using an SID and it resides in the ForeignSecurityPrincipals container. This is because Well-Known SIDs such as Everyone (S-1-1-0) and Authenticated Users (S-1-5-11) are not maintained within Active Directory itself and are therefore stored in the FSP container.


Problem

You want domain controllers to reject LDAP queries from certain IP addresses. This can be useful if you want to prohibit domain controllers from responding to LDAP queries for certain applications or hosts.

Solution

Using a command-line interface

The following adds network 10.0.0.0 with mask 255.255.255.0 to the IP deny list:

> ntdsutil “ipdeny list” conn “co t s <DomainControllerName>” q

IP Deny List: Add 10.0.0.0 255.255.255.0

*[1] 10.0.0.0 GROUP MASK      255.255.255.0

NOTE: * | D – uncommitted addition | deletion

IP Deny List: Commit

[1] 10.10.10.0 GROUP MASK 255.255.255.0

NOTE: * | D – uncommitted addition | deletion

Discussion

The IP deny list is stored as an octet string in the lDAPIPDenyList attribute of a query policy.

When the IP deny list is set, domain controllers that are using the default query policy will not respond to LDAP queries from any IP address specified in the deny list address range. To test whether a certain IP address would be denied, run Test x.x.x.x (where x.x.x.x is an IP address) from the IP Deny List subcommand in ntdsutil.

By setting the IP deny list on the default query policy, you would effectively restrict the IP address range from querying any domain controller in the forest. If you need to restrict queries only for a specific domain controller, you’ll need to create a new LDAP query policy and apply it to only the domain controller in question.

Problem

You want to enable anonymous LDAP access for clients. In Windows 2000 Active Directory, anonymous queries were enabled by default, although they were restricted. With Windows Server 2003 Active Directory, anonymous queries are disabled by default except for querying the RootDSE.

Solution

Using a graphical user interface
  1. Open ADSI Edit.

  2. In the Configuration partition, browse to cn=Services cn=Windows NT cn=Directory Service.

  3. In the left pane, right-click on the Directory Service object and select Properties.

  4. Double-click on the dSHeuristics attribute.

  5. If the attribute is empty, set it with the value 0000002.

  6. If the attribute has an existing value, make sure the seventh digit is set to 2.

  7. Click OK twice.

Problem

You want to enable SSL/TLS access to your domain controllers so clients can encrypt LDAP traffic to the servers.

Solution

Using a graphical user interface
  1. Open the Control Panel on a domain controller.

  2. Open the “Add or Remove Programs” applet.

  3. Click on Add/Remove Windows Components.

  4. Check the box beside Certificate Services and click Yes to verify.

  5. Click Next.

  6. Select the type of authority you want the domain controller to be (select “Enterprise root CA” if you are unsure) and click Next.

  7. Type the common name for the CA, select a validity period, and click Next.

  8. Enter the location for certificate database and logs, and click Next.

  9. After the installation completes, click Finish.

  10. Now open the Domain Controller Security Policy GPO.

  11. Navigate to Computer Configuration Windows Settings Security Settings Public Key Policies.

  12. Right-click on Automatic Certificate Request Settings and select New Automatic Certificate Request.

  13. Click Next.

  14. Under Certificate Templates, click on Domain Controller and click Next.

  15. Click Finish.

  16. Right-click on Automatic Certificate Request Settings and select New Automatic Certificate Request.

  17. Click Next.

  18. Under Certificate Templates, click on Computer and click Next.

  19. Click Finish.

While Windows Vista may be Microsoft Corp’s most secure operating system ever, it’s far from completely secure. In its fresh-from-the-box configuration, Vista still leaves a chance for your personal data to leak out to the Web through Windows Firewall or for some wicked bot to tweak your browser settings without your knowledge.

But by making a few judicious changes using the security tools within Windows Vista — and in some cases by adding a few pieces of free software –you can lock down your operating system like a pro.

1. Use Windows Security Centre as a starting point

For a quick overview of your security settings, the Windows Security Center is where you’ll find the status of your system firewall, auto update, malware protection and other security settings. Click Start, Control Panel, SecurityCenter, or you can simply click the shield icon in the task tray. If you see any red or yellow, you are not fully protected.

For example, if you have not yet installed an antivirus product on your machine, or if your current antivirus product is out of date, the malware section of the Security Center should be yellow. Windows does not offer a built-in antivirus utility, so you’ll want to install your own. For free antivirus,

I recommend Avast 4.8 Home Edition.

2. Use Windows Defender as a diagnostic tool

The malware section of Windows Vista also protects against spyware using Windows Defender. The antispyware protection in your antivirus program usually trumps the protection Microsoft provides, but there are several good reasons to keep Windows Defender enabled. One is that every antispyware program uses a different definition of what is and is not spyware, so redundant protection can actually offer some benefit.

Another reason to keep Windows Defender enabled: diagnostics. Click Tools, and choose Software Explorer from the resulting pane. You can display lists of applications from several categories such as Currently Running Programs, Network Connected Programs and Winsock Service Providers, but Start-u

p Programs is perhaps the most useful. Click on any name in the left window, and full details will appear in the right pane. By highlighting, you can remove, disable or enable any of the programs listed.

3. Disable the start-up menu

Windows Vista keeps track of all the documents and programs you launch in the start-up menu. This can be convenient for some users, but it can also compromise your privacy if you share a computer within an office or household. Fortunately, Windows Vista provides an easy way to tweak this setting

. To protect your privacy, follow these steps:

* Right-click on the task bar and select “Properties.”

* Click on the Start Menu tab.

* Uncheck “Store and display a list of recently opened files.”

* Uncheck “Store and display a list of recently opened programs.”

* Click “OK.”

4. Get two-way firewall protection

No desktop should be without a personal firewall, but even if the Security Center says you’re protected, you may not be. The Windows Firewall within Vista blocks all incoming traffic that might be malicious or suspicious — and that’s good. But outbound protection is not enabled by default. That’s a dangerous situation if some new malicious software finds its way onto your PC.

Microsoft did include the tools for Windows Vista to have a true two-way firewall, but finding the setting is a little complicated. (Hint: Don’t go looking the Windows Firewall settings dialog box.

To get two-way firewall protection in Windows Vista, do the following:

* Click on the Start button; in the search space, type “wf.msc” and press Enter.

* Click on the Windows Firewall with Advanced Security icon. This management interface displays the inbound and outbound rules.

* Click on Windows Firewalls Properties. You should now see a dialog box with several tabs.

* For each profile — Domain, Private and Public — change the setting to

Block, and then click OK.

Even if you do this tweak, I recommend adding a more robust third-party firewall. I suggest either Comodo Firewall Pro or ZoneAlarm, both of which are free and fare very well in independent firewall testing.

5. Lock out unwanted guests

If you share your computer with others — and even if you don’t – Windows Vista includes a neat way to keep unwanted guests from guessing your systems administrator password. When you set up users and declare one user as administrator with full privileges, Windows Vista allows an outsider unlimited guesses at the password you chose. Here’s how to limit the guesses.

* Click Start, then type “Local Security Policy.”

* Click Account Lockout Policy.

* Choose Account Lockout Threshold.

* At the prompt, enter the number of invalid log-ins you’ll accept (say, three).

* Click OK and close.

6. Now audit your attackers

With the Account Lockout policy in place, you can now enable auditing to see any account attacks. To turn on auditing for failed log-on events, do the following:

* Click the Start button, type “secpol.msc,” and click the secpol icon.

* Click on Local Policies and then Audit Policy.

* Right-click on “Audit account log-on events policy,” and select Properties.

* Check the Failure box, and click OK.

* Right-click on “Audit log-on events policy” and select Properties.

* Check the Failure box and click OK.

* Close the Local Security Policy window.

You can then use the Event Viewer (by running eventvwr.msc) to view the logs under Windows Logs and Security.

7. Secure your Internet Explorer settings

The Windows Security Center will also report whether your Internet Explorer 7(or IE 8) security settings are at their recommended levels. If the screen shows this section as red, you can adjust the settings within the browser itself.

* Within Internet Explorer, click Tools in the menu bar.

* From the drop-down menu, click Internet Options.

* Choose the Security tab.

* Within the Security tab, click Custom Level.

Here you’ll see a window with all the security options for the browser. If any are below the recommended level (if, say, some malware reconfigured your browser settings), these options will be highlighted in red.

To change an individual setting, click the appropriate radio button. To reset them all, use the button near the bottom of the tab. You can also change the overall security setting for Internet Explorer from the default Medium-High setting to the recommended High or Medium, if you wish. Click OK to save and close.

8. Use OpenDNS Domain Name System (DNS) servers act as a phone book. When you type “pcworld.com” in the address bar, for instance, your browser sends that common

-name request to your Internet service provider’s DNS servers to be converted into a series of numbers, or an IP address.

Lately, DNS servers have come under attack, with criminals seeking to redirect common DNS preferences to servers that they control. One way to stop such abuse is to use OpenDNS.

Go to Start, Control Panel, Network and Internet, and then click Network and Sharing Center. Under the tasks listed on the left, click Manage Network Connections. In the Manage Network Connections window, do the following:

* Right-click on the icon representing your network card.

* Click Properties.

* Click Internet Protocol Version 4.

* Click the Properties button.

* Select the Use the following DNS server addresses radio button.

* Type in a primary address of 208.67.222.222.

* Type in a secondary address of 208.67.220.220.

* Click OK.

9. Live with User Account Control

One area where some people might want to see the Windows Security Center turn red is User Account Control (UAC), perhaps the most controversial security feature within Windows Vista. Designed to keep rogue remote software from automatically installing (among other things), UAC has a tendency to thwart legitimate software installations by interrupting the process several times with useless messages.

In Windows 7, you’ll be able to set UAC to the level you want. Until then, you do have some options. One is to disable UAC. I would caution against that, since UAC is meant to warn you of potential danger.

Instead, install TweakUAC, a free utility that enables you to turn UAC on or off as well as provides an intermediate “quiet” mode that keeps UAC on but suppresses administration-elevation prompts. With TweakUAC in quiet mode, UAC will appear to be off to those running as administrator accounts, while people with standard user accounts will still be prompted.

10. Check your work

Now that you’ve tweaked Windows Vista, you can keep tabs on your system’s security with the System Health Report. This diagnostic tool takes input from the Performance and Reliability Monitor and turns it into an information-packed report that can spotlight potential security problems.

* Open Control Panel.

* Click System.

* In the Tasks list, click Performance (near the bottom).

* In the resulting Tasks list, click Advanced tools (near the top).

* Click the last item on the resulting list — “Generate a system health report.”

The report will list any missing drivers that might be causing error codes, tell you whether your antivirus protection is installed and declare whether UAC is turned on. You may want to run this report once a month just to make sure everything is still good.

Malware – The generic term used for all forms of software designed with malicious intent. Viruses, worms, spyware etc. are all forms of malware. The term virus is often used when malware should really be used as it describes all forms of malicious software.

Virus – A computer virus acts very much like a human virus. Human viruses are spread, via thumb drives, floppy discs, network connections etc., to other PCs. Viruses need a host (like a free screensaver program) to spread. By pure definition: a virus has the ability to spread itself, via a host, to other computers.

Worm – A worm is much like a virus. The key difference is worms can spread between PCs without a host (free screensaver program, downloaded game etc.) These programsrely on computer networks and usually damage files and slow down networks in their path.

Trojan horse (Trojan) – A Trojan horse is a seemingly harmless program that looks to provide value. However, just as in Greek mythology, a Trojan horse has a secret agenda and acts as a backdoor to your computer. This backdoor can be accessed by a hacker to compromise your PC. Trojan horses are not self-replicating and spread due to users installing them manually on their PC.

Privacy-invasive software – A formal term used to describe software that invades your privacy. This software comes in different forms including spyware and adware.

Spyware – Spyware tracks a user’s activity by monitoring browsing habits and keyboard activity and can even take screenshots while you use your PC. This information is sent back to the creator or beneficiary of the spyware. Signs of spyware include: modified browser homepages, slow internet, and suspicious looking sites in place of legitimate sites (for example: banking sites.)

Adware – Like spyware, adware is software that may track visited websites and act as a key logger. Adware tracks this information to automatically display downloaded or installed adverts to a user. You may wonder why you are being offered “PC Super Anti Spyware 2011” when using your PC; this is adware at work. AIM, FlashGet, Deamon Tools, and RealPlayer are all examples of adware.

Backdoor – A backdoor is a point of access to a computer that does not require authentication. An unlocked house back door gives access to an otherwise secure home; a computer backdoor allows access to your PC without your knowledge or permission.

Key logger – Key loggers are used to monitor keyboard activity on a PC. These can be software-based (bundled with Trojan horses, adware, and spyware) or hardware-based (between the keyboard cable and the PC, acoustic etc.) Usually this information is retrieved across a local network, the internet, or from the physical device connected to the keyboard.

Firewall – A firewall both permits and blocks access to a network or PC. Firewalls are included with popular security software (e.g. AVG Internet Security and ESET Smart Security) and limit communication between your PC and devices that are not authorized to communicate with you.

Windows Firewall – Comes bundled with Windows XP, Vista, and 7. This is a great solution; however, due to a lack of comprehensive definition updates, Windows Firewall is not completely effective in blocking threats and allowing safe connections.

Antimalware / Antivirus / Antispyware – Software designed to remove or block malware (e.g. AVG Internet Security and ESET Smart Security.)

E-Mail Spoofing

Posted: August 25, 2009 in Networking, Security
Tags: ,

Email “Spamming” and Email “Spoofing”

Two terms to be familiar with in these days of increased communication via electronic mail: email “spamming” and email “spoofing”.

Email “spamming” refers to sending email to thousands and thousands of users – similar to a chain letter. Spamming is often done deliberately to use network resources. Email spamming may be combined with email spoofing, so that it is very difficult to determine the actual originating email address of the sender. Some email systems, including our Microsoft Exchange, have the ability to block incoming mail from a specific address. However, because these individuals change their email address frequently, it is difficult to prevent some spam from reaching your email inbox.

Email spoofing refers to email that appears to have been originated from one source when it was actually sent from another source. Individuals, who are sending “junk” email or “SPAM”, typically want the email to appear to be from an email address that may not exist. This way the email cannot be traced back to the originator.

Malicious Spoofing

There are many possible reasons why people send out emails spoofing the return address: sometimes it is simply to cause confusion, but more often it is to discredit the person whose email address has been spoofed: using their name to send a vile or insulting message.

Sometimes email spoofing is used for what is known as “social engineering”, which aims to trick the recipient into revealing passwords or other information. For example, you get an email from what appears to be the LSE’s email administrator, or from your ISP, asking you to go to a Web page and enter your password, or change it to one of their choosing. Alternatively, you might receive an email asking for detailed information about a project. The From field suggests that the message comes from the LSE, but instead it is from a competitor.

Dealing with a Spoofed Email

There is really no way to prevent receiving a spoofed email. If you get a message that is outrageously insulting, asks for something highly confidential, or just plain doesn’t make any sense, then you may want to find out if it is really from the person it says it’s from. You can look at the Internet Headers information to see where the email actually originated.

Remember that although your email address may have been spoofed this does not mean that the spoofer has gained access to your mailbox.

Displaying Internet Headers Information

An email collects information from each of the computers it passes through on the way to the recipient, and this is stored in the email’s Internet Headers.

1. With the Outlook Inbox displayed, right-click on the message and click on the Optionscommand to display the Message Options dialog box.

2. Scroll to the bottom of the information in the Internet Headers box, then scroll slowly upwards to read the information about the email’s origin. The most important information follows the “Return-path:” and the “Reply-to:” fields. If these are different, the email is not who it says it’s from.

Virus spoofing

Email-distributed viruses that use spoofing, such the Klez or Sobig virus, take a random name from somewhere on the infected person’s hard disk and mail themselves out as if they were from that randomly chosen address. Recipients of these viruses are therefore misled as to the address from which they were sent, and may end up complaining to, or alerting the wrong person. As a result, users of uninfected computers may be wrongly informed that they have, and have been distributing a virus.

If you receive an alert that you’re sending infected emails, first run a virus scan using Antivirus . If you are uninfected, then you may want to reply to the infection alert with this information:

“Your virus may have appeared to have been sent by me, but I have scanned my system and I am not infected. A number of email-distributed viruses fake, or spoof, the ‘From’ address using a random address taken from the Outlook contacts list or from Web files stored on the hard drive.”

But keep in mind that a virus alert message is quite often auto generated and sent via an anti-virus server and so replying to the original email may not elicit a response.

Alternatively, if you receive an email-distributed virus, look at the Internet Headers information to see where the email actually originated from, before firing off a complaint or virus alert to the person you assume sent it.