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Published Jun 02, 2006 | Updated Sep 15, 2017

Worm:Win32/Chir.B@mm

Detected by Microsoft Defender Antivirus

Aliases: W32.Chir.B@mm (Symantec) W32/Chir.b@mm (McAfee) WORM_CHIR.B (Trend Micro)

Summary

Win32/Chir.B@mm is both a network and e-mail worm, as well as a virus. The e-mail worm component sends a copy of itself as an e-mail attachment to addresses that it finds on local and remote drives. Win32/Chir.B@mm also exploits the Incorrect Mime Header vulnerability discussed in Microsoft Security Bulletin (MS01-020). This may cause the e-mail attachment to open automatically when the e-mail is read or previewed on susceptible systems that have not had the MS01-020 security patch installed. Win32/Chir.B@mm infects .EXE and .SCR files on local and remote drives. Win32/Chir.B@mm also drops a copy of itself named readme.eml to folders containing .HTM and .HTML files, then appends malicious JavaScript to the bottom of these .HTM* files to cause them to automatically run the infected readme.eml file when they are opened.
Win32/Chir.B@mm infects .EXE and .SCR files, copies itself as Readme.exe to local and remote drives, and appends malicious Javascript to .HTM and .HTML files. For these reasons, it is not advisable to try to remove Win32/Chir.B@mm manually. Instead, use up-to-date antivirus software to remove this and other malicious software.  To remove this malicious software using antivirus software, follow these steps:
  1. Disconnect from the Internet.
  2. Run up-to-date antivirus software.
  3. Take steps to prevent re-infection.

Disconnect from the Internet  

To help ensure that your computer is not actively infecting other computers, disconnect it from the Internet before proceeding by unplugging your network cable or disabling your wireless connection. You can reconnect to the Internet after running antivirus software.

Run up-to-date antivirus software  

Run up-to-date antivirus software to remove this malicious software from your computer.

Take steps to prevent re-infection  

Do not reconnect your computer to the Internet until the computer is protected from re-infection. See the "How to Prevent Infection" section for more information.
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