Bofra.A

Threat description

Details

CATEGORYMalware
TYPEWorm

Summary

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.

Removal

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:

FREE ADULT VIDEO! SIGN UP NOW!
 

or

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:

https://www.f-secure.com/weblog/archives/archive-112004%2ehtml#00000347

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 (http://amavis.org/)
Checked for viruses by Gordano's AntiVirus Software
Checked by Dr.Web (http://www.drweb.net)
 

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.
ibm.com
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:

aol.com
msn.com
yahoo.com
hotmail.com
Backdoor

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

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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