F-secure has raised alert level of this virus to Radar LEVEL 2:
Email Worm Sober.I is spreading, mostly in Europe. It sends highly variable German and English emails with an attachment. The virus drops several files to infected systems, including spool32dir.exe.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
More information on 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.
The worm is written in Visual Basic. The worm's file is a UPX packed PE executable with length of 56 KiBytes.
Installation to system
When the worm's file is started it shows the following messagebox:
Then the worm installs itself to system. It makes two copies itself to Windows System folder with a semi-randomly generated name and EXE extension. The following text strings are used to generate the file names of the worm's executable:
sys host dir expoler win run log 32 disc crypt data diag spool service smss32
After that the worm creates startup keys for its files in Windows Registry. The key names are also semi-randomly generated from the above given list. The following keys are created:
" = "%WinSysDir%\ .exe" [HKCU\Software\Microsoft\Windows\CurrentVersion\Run] " " = "%WinSysDir%\ .exe %srun%" [HKLM\Software\Microsoft\Windows\CurrentVersion\Run] " " = "%WinSysDir%\ .exe" [HKLM\Software\Microsoft\Windows\CurrentVersion\Run] " " = "%WinSysDir%\ .exe %srun%"
During its installation cycle the worm creates the following files in Windows System folder:
dgssxy.yoi sysmms32.lla cvqaikxt.apk Odin-Anon.Ger
These files have zero length and they are used to disable previous variants of Sober if they are installed on an infected computer.
Additionally the worm creates the following files:
clonzips.ssc clsobern.isc nonzipsr.noz zippedsr.piz
These files are MIME-encoded copies of the worm's executable file and a ZIP archive with the worm's file. These files will be used for spreading of the worm in e-mail messages.
Spreading in e-mails
The worm sends e-mail messages with English and German texts and its file attached. The attached file can be an executable or a ZIP archive containing the worm's executable. The worm composes several different types of messages and the content of these messages is variable. Here's an example of a English message sent by the worm:
Before spreading the worm scans files with certain extensions on all hard disks to harvest e-mail addresses. Files with the following extensions are scanned:
pmr stm slk inbox imb csv bak imh xhtml imm imh cms nws vcf ctl dhtm cgi pp ppt msg jsp oft vbs uin ldb abc pst cfg mdw mbx mdx mda adp nab fdb vap dsp ade sln dsw mde frm bas adr cls ini ldif log mdb xml wsh tbb abx abd adb pl rtf mmf doc ods nch xls nsf txt wab eml hlp mht nfo php asp shtml dbx
The found e-mail addresses and user names are saved in these 2 files that the worm created in Windows System folder:
When the worm is active in memory it blocks access to these files as well as to its MIME-encoded files and its executable file.
The worm ignores e-mail addresses that contain any of the following substrings:
1-000000-000000 tps@ hubak@ ruiv@ farbugs@ ron@ info@ sales@ press@ ventes@ rar.dutch@ rar@ vmlich@ jimaz@ RAR.regsite@ provision@ alex@ webmaster@ rod@ selwyn_arrow@ admin@ inftec@ eugene@ jwpark@ sam@ sites.far@ whatsnew.far@ helpdesk@ fararcbugs@ mark@ cogswell@ licensing@ apply@ Ollydbg@ snaker@ mail@ qwaci@ g-rom@ lorian@ stone@ GOD@ tac_2000@ tac_cracking@ mackt@ christoph@ - rarsoft.com rarsoft.de yahoo.com
If the worm sends infected messages to domains with suffixes '.de', '.ch', '.at', '.li' or to 'gmx.' domain, it composes messages in German, otherwise English messages are composed.
The worm can compose English messages from the following text string arrays:
Subject (one of the following):
Details God it's Registration confirmation Confirmation Your Password Your mail password Delivery failure notice Faulty mail delivery Mail delivery failed Mail Error illegal signs in your mail invalid mail Mail Delivery failure mail delivery system
Message body (one of the following):
I was surprised, too! Who could suspect something like that? shity Your password was changed successfully! Protected message is attached! This mail was generated automatically. More info about --[domain]-- under http:// [domain]
Attachment name (one of the following):
im_shocked thats_hard oh_nono user_info new_account info hostmaster corrected full original re_mail auto_mail mail
Sober's attachment name can contain a random number and can have one of the following extensions:
.com .bat .pif .scr
Also the attachment can be sent in a ZIP archive. In this case the worm's file inside the archive will have double extension. The first extension is selected from the following list:
.txt .doc .word .xls .eml
The subject of an infected e-mail can have 'FwD:' or 'Re:' string.
Sober.I can place a fake anti-virus scanner report in the message body trying to persuade a recipient that the message was scanned by an on-line scanner and no infection was found.
This Sober variant is detected with FSAV updates:
Detection Type: PC
Description Details: Katrin Tocheva; November 19th, 2004
Technical Details:Jarkko Turkulainen; November 19th, 2004