Threat description




Bofra.A worm appeared on November 10th, 2004. This worm exploits an unpatched vulnerability in Internet Explorer's IFRAME handling. Unlike regular mass-mailing worms, Bofra.A does not send itself in the emails, only an HTTP link that points to the host that sent the infected email.

As a payload Bofra.A has an IRC-controlled backdoor that allows the worm's author to download and execute arbitrary programs on the compromised host.


Automatic action

Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.

More scanning & removal options

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 more information.

Contact Support

F-Secure customers can request support online via the Request support or the Chat forms on our Home - Global site.

Technical Details

The worm's body is a Windows PE executable file compressed with the MEW executable compressor and was patched by PE_Patch utility.

System Infection

When the worm's file is run, it copies itself to Windows System Folder with a random name ending in '32.exe' (for example pmbperim32.exe) and creates a startup key for this file in the Registry:

[HKLM\Software\Microsoft\Windows\CurrentVersion\Run]  "Rhino" = "%SystemDir%\[randomname]32.exe"   

where "%SystemDir%" represents the Windows System folder name, for example "C:\Windows\System32\" on Windows XP systems.

Email Propagation

To gather email addresses Bofra.A searches the Windows Address Book, files in Temporary Internet File and other files on the hard disk that have the following strings in their name:

wab  pl  adb  tbb  dbx  asp  php  sht  htm  txt   

Using its own SMTP engine Bofra.A sends emails to the collected addresses. Sender of the mails is spoofed and the content is randomly chosen from the following components:

Email subjects:

funny photos :)  hello  hey!   

Email bodies contain an HTML-formatted text:



Look at my homepage with my last webcam photos!   

The email does not have any attachments. The worm only sends the link which points to the infected host. The format of the link is

https://[infected host ip]:port/[file_to_dowload]

Bofra.A, running on the infected host, has a stripped-down web servers listening on TCP ports starting from 1638 (0x666). The only purpose of these is to serve the potential targets with the HTML page that contains the exploit as well as the worm executable that the exploit will download.

The way this propagation technique works in explained in our weblog:

The emails sent by Bofra.A contain a fake virus scanner header (X-AntiVirus:) that might get one of the following values:

scanned for viruses by AMaViS 0.2.1 (  Checked for viruses by Gordano's AntiVirus Software  Checked by Dr.Web (   

The worm avoids posting to e-mail addresses that contain certain strings:

avp  syma  icrosof  msn.  hotmail  panda  sopho  borlan  inpris  example  mydomai  nodomai  ruslis  .gov  gov.  .mil  foo.  berkeley  unix  math  bsd  mit.e  gnu  fsf.  google  kernel  linux  fido  usenet  iana  ietf  rfc-ed  sendmail  arin.  ripe.  isi.e  isc.o  secur  acketst  pgp  tanford.e  utgers.ed  mozilla  root  info  samples  postmaster  webmaster  noone  nobody  nothing  anyone  someone  your  you  me  bugs  rating  site  contact  soft  no  somebody  privacy  service  help  not  submit  feste  ca  gold-certs  the.bat  page  admin  icrosoft  support  ntivi  unix  bsd  linux  listserv  certific  google  accoun   

The worm fakes the sender's address. It uses the following list of names to compose the fake address:

john  john  alex  michael  james  mike  kevin  david  george  sam  andrew  jose  leo  maria  jim  brian  serg  mary  ray  tom  peter  robert  bob  jane  joe  dan  dave  matt  steve  smith  stan  bill  bob  jack  fred  ted  adam  brent  alice  anna  brenda  claudia  debby  helen  jerry  jimmy  julie  linda  sandra   

The worm uses the following list of domain names to compose the fake sender's address:  

As a payload Bofra.A has an IRC-controlled backdoor that allows the worm's author to download and execute arbitrary programs on the compromised host.


Detection for Bofra.A was published on November 10th, 2004 in the following F-Secure Anti-Virus update:

Detection Type: PC

Database: 2004-11-10_03

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