W32.Aplore@mm

SUMMARY

W32.Aplore@mm is a mass-mailing worm that attempts to spread using email, IRC, and AOL Instant Messenger (AIM).

The worm sends an email that contains an attachment, Psecure20x-cgi-install.version.6.01.bin.hx.com, to all addresses that it finds in the Microsoft Outlook address book.

When connected to IRC or AIM, the worm sends a Web link to IRC channels or AIM contacts which references an .html file that was dropped on the infected computer. This file displays as a Web page, which asks the visitor to run a copy of the worm.

Behavior

Symptoms

Transmission

Protection

• Virus Definitions (LiveUpdate™ Weekly) April 10, 2002
• Virus Definitions (Intelligent Updater) April 8, 2002

Threat Assessment

Wild

• Wild Level: Medium
• Number of Infections: 50 - 999
• Number of Sites: 3 - 9
• Geographical Distribution: Medium
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Low
• Large Scale E-mailing: Yes

Distribution

• Distribution Level: High
• Subject of Email: .
• Name of Attachment: Psecure20x-cgi-install.version.6.01.bin.hx.com
• Size of Attachment: 319,488 Bytes

TECHNICAL DETAILS

When the worm is executed by running the file Psecure20x-cgi-install.version.6.01.bin.hx.com, it does the following:

1. It copies itself as:
   • \%System%Explorer.exe
   • \%System%Psecure20x-cgi-install.version.6.01.bin.hx.com
     
     NOTE: %System% is a variable. The worm locates the WindowsSystem folder (by default this is C:WindowsSystem or C:WinntSystem32) and copies itself to that location.
     
2. It adds the value
   
   Explorer       %SYSTEM%Explorer.exe
   
   to the registry key
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindows
   CurrentVersionRun
   
   so that it runs when you start Windows.
   
3. Next, it drops the file \%System%Email.vbs. It then uses Microsoft Outlook to spread itself. The email has the following characteristics:
   
   Subject: .
   Message: .
   Attachment: Psecure20x-cgi-install.version.6.01.bin.hx.com
   
   NOTE: The subject and message each consist of only a period.
   
4. It drops the file \%System%Index.html. It then attempts to run Psecure20x-cgi-install.version.6.01.bin.hx.com from the System folder by using a refresh tag in the dropped .html file. The following .html message appears:
   
   Browser Plugin Required:
   
   You may need to restart your browser for changes to take affect.
   Security Certificate by Verisign 2002.
   MD5: 9DD756AC-80E057FC-E00703A2-F801F2E3
   
   Click HERE and choose "Run" to install.
   
5. It drops the file WindowsAphex.jpg.
6. Finally, it attempts to spread itself using IRC or AOL Instant Messenger ()AIM.

AOL Instant Messenger (AIM) functionality
Once the worm is active on the infected computer, it acts as an HTTP server on port 8180. This server hosts one Web page. The page displays the text that is mentioned in step 4 of the previous section.

The worm waits for you to connect to AIM; it then sends one of the following one-line messages to your AIM contacts:

• btw, download this,
• I wanted to show you this,
• please check out,
• hey go to,
• see if you can get this to work,
• this is cool,
• tell me what you think about,
• try this,
• I almost forgot about,
• I like this,
• what about,
• have you seen,
• interestin,
• lol,
• wow,
• whoa,
• neat,
• cool,
• hmm,
• psst,
• hehe,
• haha,
• silly,
• weird,

The message also includes a link, which references the hosted Web page, to the (now infected) computer. This functions only with the AOL software that is used with an AOL subscription. This does not function with the stand-alone AIM client.

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
• Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. Perform a forensic analysis and restore the computers using trusted media.
• Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.

REMOVAL

NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Update the virus definitions, and then restart the computer in Safe mode. Run a full system scan, and delete all files that are detected as W32.Aplore@mm.
2. Delete the value
   
   Explorer       %SYSTEM%Explorer.exe
   
   from the registry key
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   

For details on how to do this, read the following instructions.


To scan for and delete the infected files:

1. Obtain the most recent virus definitions. There are two ways to do this:
   • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
   • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions have undergone full quality assurance testing by Symantec Security Response. They are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.
     
     Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.
     
2. Restart the computer in Safe mode. All Windows 32-bit operating systems except Windows NT can be restarted in Safe mode. For instructions on how to do this, read the document How to start the computer in Safe Mode.
3. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
   • Norton AntiVirus Consumer products: Read the document How to configure Norton AntiVirus to scan all files.
   • Symantec Enterprise antivirus products: Read the document How to verify a Symantec Corporate antivirus product is set to scan All Files.
4. Run a full system scan.
5. If any files are detected as infected by W32.Aplore@mm, click Delete.

To edit the registry:

CAUTION: We strongly recommend that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.

1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. Navigate to the following key:
   
   HKEY_Local_MachineSoftwareMicrosoftWindows
   CurrentVersionRun
   
4. In the right pane, delete the following value:
   
   Explorer       %SYSTEM%Explorer.exe
   
5. Exit the Registry Editor.