A new Sober.E worm was found in Germany on Sunday March 28th, 2004. The worm replaces the 'From:' filed so the infected email looks like it comes from @gmx.net or @gmx.de address. The size of the worm's file is 30720 bytes (PIF file) or 30866 bytes (ZIP archive).
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
The worm is written in Visual Basic. The worm's file is a PE executable 30720 bytes long packed with a modified version of UPX file compressor. The worm has its own SMTP engine that it uses to send out infected e-mail messages.
The worm changes one byte at offset 0xA0 in its file upon installation to system, but the file it sends out is unchanged.
Some of the worm's text strings are encrypted and they are decrypted only before being used.
Installation to system
When the worm's file is started on a clean system, it opens Paintbrush or Microsoft Paint application as a disguise.
Then the worm installs itself to system. It copies itself to Windows System folder once, with a semi-randomly generated name and creates 2 startup keys for this file in System Registry. The worm uses the following fixed text strings to generate the name of its file and the name of the startup key:
sys host dir explorer win run log 32 disc crypt data diag spool service smss32
The worm creates a file named WINRUN32.DLL, where it stores all e-mail addresses harvested from an infected computer. The worm also creates 2 empty files in the same folder:
Additionally the worm creates 2 mime-encoded copies of its executable file and a ZIP archive in Windows System folder with the following names:
The worm creates 2 startup Registry keys its semi-randomly named file in System Registry:
The subkey name that is created by the worm is semi-randomly generated too. The value of a subkey is the path the worm's file in Windows System folder.
Spreading in e-mails.
The worm scans files with certain extensions on all hard disks to harvest e-mail addresses. Files with the following extensions are scanned:
ini log mdb tbb abd adb pl abx rtf doc xls txt wab eml php asp shtml dbx
The worm saves all found e-mail addresses to WINRUN32.DLL file located in Windows System folder. This is an ASCII file, not a binary file.
Sober.E worm spreads itself in e-mails as an executable attachment or inside a ZIP archive. The worm uses the following strings as the subject line:
Hi hi Hi :-) Ok :-) OK OK Ok ok OK! Hey! hey? HEY
The message body can contain the following strings:
thx Thx! THX ;-) ha! HA yo! lol LoL LOL Yo!
The attachment name can consist of the following strings and a randomly generated number:
text read Graphic-doc document worm
The attachment has either PIF or ZIP extension. The worm's executable file name inside the archives that we've received so far is:
To send e-mails the worm uses the following mail servers:
The worm fakes the sender's e-mail address. The fake address is composed by the worm from the following strings:
aRuder g.rulers S.Serger Dude-X777 Nicole.Pam R.Summer T.Welder Susan.Ewing E.Ruders Blond.Sybil Michelle.Horn Sabine.S-1977 E.Juller Pamela-S J.Moders Regina-1978 BMueller4 Elsbeth.Sinker Thomas.Schmahler Nikki.1978 D.Rotter Patricia.1979 S.Loltke Patty.Geldorf H.Molma Birgit.Muse Peter.Selders Johanna.1980 Nicole.Gellert R.Niere P.Schulz1 Kalif.Rent Herbert.Weed FParker Samatha.Kelis Kate.Lee Bibi.Besen Julia.Witt1 Alexander.Bendher Rosemarie.Hetter A.Rebert Elke.Duerr D.Winter1 Angelika.Neum A.Kempen KevinEder Susan.Leet Friedhelm.alt Seth.Liveima Eileen.Leen D.Augustam B.Kaine MikeLord Kathe.Meet Marie.Dreher Tom.Schon Lisa.Redfield R.Kleinmaurer A.Mack1 Jundel b.sieber006 Ulrike.Falkner C.Poller
The following domain names are selected for the fake sender's address:
The worm avoids sending infected messages to e-mail addresses that contain any of the following:
bigfoot hotmail online web accor yahoo gmx aol msn
Sober.E worm constantly checks a hard drive for the presence of the file named ZHCARXXI.VVX. If this file is found, the worm unloads itself from memory. Also if this file is present on a hard disk during the worm's installation process, the worm does not copy itself to a hard drive.
The worm can download and run an executable file from the following websites:
The name of the downloaded file is:
The worm tries to contact several NTP servers that are hardcoded it its body:
Rolex.Peachnet.edu ntps1-1.cs.tu-berlin.de ntp2.fau.de ptbtime2.ptb.de time.nrc.ca ntp.metas.ch ntps1-0.cs.tu-berlin.de ntp0.fau.de timelord.uregina.ca ntp-1.ece.cmu.edu ptbtime1.ptb.de time.ien.it ntp3.fau.de time.chu.nrc.ca clock.psu.edu ntp1.fau.de
Detection of Sober.E worm is available in the following FSAV updates:
Detection Type: PC
Description Created: Katrin Tocheva, March 28th, 2004
Technical Details: Alexey Podrezov; March 28th, 2004
Description Last Modified: Alexey Podrezov; March 29th, 2004