A new variant of MyDoom worm - Mydoom.AM, was found on January 25th, 2005. It spreads in emails with different subject and body texts, and attempts to spread in several P2P networks.
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The worm is a PE executable file 32768 bytes long packed with UPX file compressor. The unpacked file's size is over 76 KiB.
When run, the worm drops a file "Mes#wtelw" in temporary folder and writes some random data in the file. Then it opens this file in notepad as a decoy.
After the notepad is closed, the worm creates a mutex named "-=RTSW.Smash 0a2a0=-" and copies itself as
where %Sysdir% is the Windows system directory. On default install of Windows XP, that is c:\Windows\system32. It also drops the following files:
version.ini contains supposedly the worm version number (0.20) and hserv.sys is encrypted data file containing web sites the worm contacts for instructions.
The worm installs the following registry keys:
This will ensure that the worm will be started on next Windows startup.
The worm spreads by sending its infected attachment to all email addresses found on an infected computer. The worm looks for email addresses in Windows Address Book and in the files with the following extensions:
The worm avoids sending emails to email addresses that contain any of the following substrings:
The subject of infected emails is selected from the following variants:
The body of the emails can one of the following:
Mail transaction failed. Partial message is available. The message contains Unicode characters and has been sent as a binary attachment. The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment. Attention! New self-spreading virus! Be careful, a new self-spreading virus called "RTSW.Smash" spreading very fast via email and P2P networks. It's about two million people infected and it will be more. To avoid your infection by this virus and to stop it we provide you with full information how to protect yourself against it and also including free remover. Your can find it in the attachment. (c) 2004 Networks Associates Technology, Inc. All Rights Reserved New terms and conditions for credit card holders Here a new terms and conditions for credit card holders using a credit cards for making purchase in the Internet in the attachment. Please, read it carefully. If you are not agree with new terms and conditions do not use your credit card in the World Wide Web. Thank you, The World Bank Group (c) 2004 The World Bank Group, All Rights Reserved Thank you for registering at WORLDXXXPASS.COM All your payment info, login and password you can find in the attachment file. It's a real good choise to go to WORLDXXXPASS.COM Attention! Your IP was logged by The Internet Fraud Complaint Center Your IP was logged by The Internet Fraud Complaint Center. There was a fraud attempt logged by The Internet Fraud Complaint Center from your IP. This is a serious crime, so all records was sent to the FBI. All information you can find in the attachment. Your IP was flagged and if there will be anover attemption you will be busted. This message is brought to you by the Federal Bureau of Investigation and the National White Collar Crime Center
The worm sends itself as an attachement, using one of the following names:
with one of the following extensions appended:
The worm will copy itself in folders used by Kazaa, Morpheus, iMesh, eDonkey and Limewire. It uses of the following filenames:
with one of the following extensions appended:
The worm tries to contact several web sites and download instructions. These can instruct the worm to download and execute additional files.
The worm modifies the hosts file on infected computer so that domains belonging to Anti-Virus companies and other commercial sites are resolved to the IP address 127.0.0.1, disabling the domain. The following domains are affected:
It also tries to terminate several Firewall and Anti-Virus related processes.
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