This type of worm is embedded in an e-mail attachment, and spreads using the infected computer's e-mailing networks.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.
You may also refer to the Knowledge Base on the F-Secure Community site for further assistance.
If the infection is in a local network, please follow the instructions on this webpage:
Caution: Manual disinfection is a risky process; it is recommended only for advanced users.
Manual disinfection of Mydoom consists of the following steps:
Email-Worm:W32/Mydoom.B is an e-mail worm that is capable of launching attacks against two websites, www.sco.comand www.microsoft.com. The worm also prevents infected machines from accessing anti-virus sites, including www.f-secure.com.
Mydoom.B is a variant of the Mydoom worm. It uses the same scrambling technique as the previous variant, ROT13, and shares most of its features. The worm contains this message, which is never displayed:
The following picture briefly shows the structure of the Mydoom.B worm, which can be appreciated in full detail in the PDF graph available here.
Mydoom.B, was found spreading on January 28th, 2005. The worm has a limited lifespan: it is coded to exit immediately when run after 1st of March 2004 at 03:18:42 (UTC)
It will copy itself to the following location:
And will add the following registry entries:
or, if it fails:
It drops its backdoor component, encoded in its body and packed with UPX as:
This is loaded under Explorer from this registry key:
The worm will create a mutex with the name "sync-v1.01__ipcmtx0" to ensure only one instance of itself is running at the same time.
Once run it will look for the previous variant, Mydoom.A, and will terminate its process and delete "shimgapi.dll".
The worm has the ability of sending itself to already infected computers. It will do so by first finding them through a network scan, where IP addresses will be randomly forged (skipping some invalid ranges). Then a connection attempt is made to port 3127 (opened by previous variant's backdoor), if the machine is found infected then the worm transfers itself and will be executed immediately, thereby updating the infected computers to the new version without the need for the user to receive the worm through e-mail.
Additionally, the worm will request the infected computer's hostname through gethostbyname(), resolve its IP and scan for other infected computers in the same range.
The worm will perform a Distributed Denial of Service (DDoS) attack against www.microsoft.com on 3rd of February 2004 at 13:09:18 (UTC) and www.sco.com on 1st of February 2004 at 16:09:18 (UTC).
The DDoS attack launches 8 threads against www.sco.comevery 1024 milliseconds.
The other DDoS attack launches 14 threads against www.microsoft.com every 1024 milliseconds.
The hosts file in the infected machines will be modified so that domains belonging to Anti-Virus companies and other commercial sites are resolved to the IP address 0.0.0.0, rendering them inaccessible. The file is encrypted within the worms code and contain the following:
An additional line is added before the the date when attack against Microsoft begins:
Which will make the site inaccessible. The 3rd of February the entry will be removed so the attack can be performed, which will probably cause some difficulties reaching it, if the DDoS is successful.
The modifications in the hosts file are probably targeted so that customers of the most widespread Anti-Virus products can't download new updates to disinfect the worm.
The following filenames are used in this variant when copying itself to Kazaa
And extensions chosen from:
The e-mail messages sent by the worm have the following characteristics: Subjects can be any of the following:
The body text can be one of the following:
Attachments are composed combining the following names:
with the following extensions:
As with older Mydoom variants, Mydoom.B collects addresses from Windows' Address Book and from files with extension:
It will try to avoid anti-spam tricks used by people to obfuscate e-mails addresses in webpages.
Once an address is chosen from the list of harvested addresses, the worm will send an e-mail to addresses in the same domain but to accounts like:
It will avoid sending itself to e-mail addresses containing the following account names: