W32.Sobig.F@mm

Due to the number of submissions received from customers, Symantec Security Response has upgraded this threat to a Category 4 from a Category 3 threat as of August 21, 2003.

W32.Sobig.F@mm is a mass-mailing, network-aware worm that sends itself to all the email addresses it finds in the files that have the following extensions:

.dbx
.eml
.hlp
.htm
.html
.mht
.wab
.txt

The worm uses its own SMTP engine to propagate and attempts to create a copy of itself on accessible network shares, but fails due to bugs in the code.

Email routine details
The email message has the following characteristics:

From: Spoofed address (which means that the sender in the "From" field is most likely not the real sender). The worm may also use the address <A HREF="mailto:admin@internet.com">admin@internet.com</A> as the sender.

NOTES:
The spoofed addresses and the Send To addresses are both taken from the files found on the computer. Also, the worm may use the settings of the infected computer's settings to check for an SMTP server to contact.
The choice of the internet.com domain appears to be arbitrary and does not have any connection to the actual domain or its parent company.

Subject:
Re: Details
Re: Approved
Re: Re: My details
Re: Thank you!
Re: That movie
Re: Wicked screensaver
Re: Your application
Thank you!
Your details

Body:
See the attached file for details
Please see the attached file for details.

Attachment:
your_document.pif
document_all.pif
thank_you.pif
your_details.pif
details.pif
document_9446.pif
application.pif
wicked_scr.scr
movie0045.pif

NOTES:
The worm de-activates on September 10, 2003. The last day on which the worm will spread is September 9, 2003.
W32.Sobig.F@mm uses a technique known as "email spoofing," by which the worm randomly selects an address it finds on an infected computer. For more information on email spoofing, see the "Technical Details" section below.

Symantec Security Response has developed a removal tool to clean the infections of W32.Sobig.F@mm.

Also Known As: Sobig.F [F-Secure], W32/Sobig.f@MM [McAfee], WORM SOBIG.F [Trend], W32/Sobig-F [Sophos], Win32.Sobig.F [CA], I-Worm.Sobig.f [KAV]

Type: Worm
Infection Length: about 72,000 bytes

Systems Affected: Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows XP
Systems Not Affected: Linux, Macintosh, OS/2, UNIX, Windows 3.x

Large scale e-mailing: Sends email to addresses collected from files with the following extensions: .wab, .dbx, .htm, .html, .eml, .txt.
Releases confidential info:

May steal system information, including passwords.

When W32.Sobig.F@mm is executed, it performs the following actions:

Copies itself as %Windir%winppr32.exe.

NOTE: %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:Windows or C:Winnt) and copies itself to that location.

Creates the file, %Windir%winstt32.dat.

Adds the value:

"TrayX"="%Windir%winppr32.exe /sinc"

to the registry key:

HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun

so that the worm runs when you start Windows.

Adds the value:

"TrayX"="%Windir%winppr32.exe /sinc"

to the registry key:

HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun

so that the worm runs when you start Windows.

Enumerates any network shares to which the infected computer has write access. The worm uses standard Windows APIs to do this.

NOTE: Due to a bug in the code, the worm does not copy over network shares.

Sobig.F can download arbitrary files to an infected computer and execute them. The author of the worm has used this functionality to steal confidential system information and to set up spam relay servers on infected computers.

This functionality may also be used as a worm self-update feature. Under the correct conditions, Sobig.F attempts to contact one of the list of master servers, which the author of the worm controls. Then, the worm retrieves a URL that it uses to determine where to get the Trojan file, downloads the Trojan file to the local computer, and then executes it.

In Sobig.F, the conditions for this download attempt are:
According to UTC time, the day of the week must be Friday or Sunday.
According to UTC time, the time of day must be between 7 P.M. and 10 P.M.

Sobig.F obtains the UTC time through the NTP protocol, by contacting one of several possible servers on port 123/udp (the NTP port).

The worm starts the download attempt by sending a probe to port 8998/udp of the master server. Then, the server replies with a URL, where the worm can download the file to execute.

Sobig.F also opens the following ports:
995/udp
996/udp
997/udp
998/udp
999/udp

And, it listens for any incoming UDP datagrams on these ports. Incoming datagrams are parsed, and upon receiving a datagram with the proper signature, the master server list of the worm may be updated.

Network administrators should do the following:
Block inbound traffic on ports 99x/udp.
Block outbound traffic on port 8998/udp.
Monitor NTP requests (port 123/udp), as these could be coming from infected computers. (The frequency of such checks for an infected computer should be once per hour.)

Email spoofing
W32.Sobig.F@mm uses a technique known as "spoofing," by which the worm randomly selects an address it finds on an infected computer. The worm uses this address as the "From" address when it performs its mass-mailing routine. Numerous cases have been reported in which users of uninfected computers received complaints that they sent an infected message to another individual.

For example, Linda Anderson is using a computer infected with W32.Sobig.F@mm. Linda is neither using an antivirus program nor has the current virus definitions. When W32.Sobig.F@mm performs its email routine, it finds the email address of Harold Logan. The worm inserts Harold's email address into the "From" portion of an infected message, which it then sends to Janet Bishop. Then, Janet contacts Harold and complains that he sent her an infected message; however, when Harold scans his computer, Norton AntiVirus does not find anything, because his computer is not infected.

Symantec Recommends

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.

If a blended threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.

Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
Isolate infected computers quickly to prevent further compromising your organization. Perform a forensic analysis and restore the computers using trusted media.

Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.

Removal using the W32.Sobig.F@mm Removal Tool

Symantec Security Response has developed a removal tool to clean the infections of W32.Sobig.F@mm. This is the easiest way to remove this threat and should be tried first.

Get IT Here - <A HREF="http://securityresponse.symantec.com/avcenter/venc/data/w32.sobig.f@mm.removal.tool.html"><A HREF="mailto:http://securityresponse.symantec.com/avcenter/venc/data/w32.sobig.f@mm.removal.tool.htm">http://securityresponse.symantec.com/avcenter/venc/data/w32.sobig.f@mm.removal.tool.htm</A>l</A>