Sobig.F is a mass-mailer worm which was found in the wild on
19th of August, 2003. This worm sends massive amounts of mail
with forged sender information.
The worm contains a payload that activates on Fridays and
Sundays when it downloads some program and runs it on the
infected computer.
Update on September 10th
F-Secure is downgrading the alert level on Sobig.F since it reached
its deadline.
The worm was programmed to stop spreading after September 10th, 2003.
Disinfection Tool
F-Secure provides a special tool to disinfect the Sobig.F worm. The
tool and disinfection instructions are available at:
http://www.f-secure.com/tools/f-sobig.zip
http://www.f-secure.com/tools/f-sobig.txt
http://www.f-secure.com/tools/f-sobig.exe
http://www.f-secure.com/tools/f-sobig.jar
You can also download them from our FTP server:
ftp://ftp.f-secure.com/anti-virus/tools/f-sobig.zip
ftp://ftp.f-secure.com/anti-virus/tools/f-sobig.txt
ftp://ftp.f-secure.com/anti-virus/tools/f-sobig.exe
ftp://ftp.f-secure.com/anti-virus/tools/f-sobig.jar
Sobig.F spreads in compressed form, packed with TELock. The
unpacked body is around 100 kilobytes in size, which was compiled
with Visual C++.
System infection
The worm will install itself into:
%windir%\winppr32.exe
Proceeding then to add the following keys to the Windows Registry:
[HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
"TrayX" = %windir%\winppr32.exe /sinc
[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
"TrayX" = %windir%\winppr32.exe /sinc
So it's started when Windows does.
Deactivation routine
The worm will stop spreading on 10th of September 2003. From this date
onwards it will exit immediately when executed.
Mail spreading
Sobig.F usually arrives in e-mails with the following characteristics:
From:
The 'From:' field is filled with an address found from the infected system.
If no address is found, it will use "admin@internet.com"
To:
The 'To:' field is filled with an address found from the infected system.
Subject, any from the list:
Re: Thank you!
Thank you!
Your details
Re: Details
Re: Re: My details
Re: Approved
Re: Your application
Re: Wicked screensaver
Re: That movie
Body, it chooses one from the two following lines:
See the attached file for details
Please see the attached file for details.
Attachment names can be any from:
your_document.pif
document_all.pif
thank_you.pif
your_details.pif
details.pif
document_9446.pif
application.pif
wicked_scr.scr
movie0045.pif
Sometimes the attachment is missing.
Also, the mail header always contains this string: "X-MailScanner: Found to be clean".
Do note that there's an anti-virus product which inserts this header to emails.
Trojan downloader
The worm will also attempt to fetch a URL from where to download components
when certain conditions are met. The condition, in this case, is that the time
which is obtained from one the NTP servers (which addresses it has hard-coded
inside its code) is Friday or Sunday (regardless of the week) between 19:00 and
22:00 UTC time. The worm will perform this test every hour.
When the condition meets, it will attempt to retrieve an URL from a predefined
list of 20 master hosts. The content of the URL will be downloaded and executed
on the infected machines.
The list of NTP servers, used to coordinate the download of the URL is:
(This is not the list of master servers)
200.68.60.246
62.119.40.98
150.254.183.15
132.181.12.13
193.79.237.14
131.188.3.222
131.188.3.220
193.5.216.14
193.67.79.202
133.100.11.8
193.204.114.232
138.96.64.10
chronos.cru.fr
212.242.86.186
128.233.3.101
142.3.100.2
200.19.119.69
137.92.140.80
129.132.2.21
Update on the activation: August 22nd, 16:00 UTC
Sobig.F activates on Friday the 22nd of August at 19:00
UTC. For information on this, please see:
http://www.f-secure.com/news/items/news_2003082200.shtml
F-Secure can confirm that 18 of the 20 master servers are currently down
or unreachable.
Update on the activation: August 22nd, 17:00 UTC
F-Secure can confirm that 17 of the 20 master servers are currently down.
Apparently one of the machines was not disconnected by an ISP and has been
booted up by its owner.
We're working together with CERTs, FBI and Microsoft to stop the last
three.
Update on the activation: August 22nd, 18:00 UTC
F-Secure can confirm that ALL the master server machines are currently
down or unreachable. One of them seems to still respond to PING but not to 8998 UDP.
We have one hour to go to see if this really is the case.
Update on the activation: August 22nd, 18:20 UTC
Unfortunately one server is up right now after all. And one might be enough for the
attack to start succesfully.
Update on the activation: August 22nd, 19:00 UTC
When deadline for the attack was passed, one machine was still (somewhat) up.
However, immediately after the deadline, this machine (located in the USA) was
totally swamped under network traffic.
We've tried connecting to it, just like the virus does. We do this from three
different sensors from three different machines in three different countries.
We haven't been able to connect to it once. If we can't connect, neither can
the viruses.
So the attack failed.
We'll keep monitoring until 22:00 UTC. If we're not able to connect once,
we can safely say that the attack was prevented.
Update on the activation: August 24nd, 19:50 UTC
Still not a single connection from any of our sensors to any of the servers.
Update on the activation: August 24nd, 21:30 UTC
Situation is still the same. Things look good.
Update on the activation: August 24nd, 22:00 UTC
The official attack time on Friday has ended. All 20 machines were inaccessible
throughout the attack.
Now we are investigating random UDP traffic that has been seen in the net, possibly
relating to the worm.
Update on the activation: August 24th, 19:00 UTC
Sobig.F activates on Sunday the 24th of August at 19:00 UTC
Currently all master servers are down, nothing is likely to happen.
Update on the activation: August 24nd, 20:30 UTC
The situation remains the same.
Update on the activation: August 24nd, 22:00 UTC
Nothing happened - the attack failed again.
Update on the activation: August 29th, 19:00 UTC
Sobig.F activates on Friday the 29th of August at 19:00 UTC
All the master servers are down.
Update on the activation: August 29th, 22:20 UTC
All master servers are down. Nothing happened during the three hour
period. The attack failed.
Sobig history
The following table shows all the Sobig variants, with their expiration
dates and when they were first found in the wild. The "Detection" field
refers to when we first had databases which detected the corresponding
variant.
Variant Found Expires Detection
_____________________________________________________________
Sobig.A January 9th NO 2003-01-09_04
Sobig.B May 18th May 31st 2003-05-19_03
Sobig.C May 31st June 8th 2003-06-01_01
Sobig.D June 18th July 2nd 2003-06-18_03
Sobig.E June 25th July 14th 2003-06-26_02
Sobig.F August 19th September 10th 2003-08-19_02
_____________________________________________________________
Detection
F-Secure Anti-Virus detects the worm with:
[FSAV_Database_Version]
Version=2003-08-19_02
Technical Details:
Ero Carrera
Description Updated:
Veli-Jussi Kesti, Mikko Hypponen, Katrin Tocheva, Gergely Erdelyi
F-Secure Corporation, August 19th - September 10th, 2003
![](/images/pixel.gif"){kind=tracking}
