Sober.N email worm was found on 19th of April, 2005. It sends itself as an attachment in e-mail messages with English or German texts.
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 modified UPX packed PE executable about 73 kilobytes long.
The worm sends different types of e-mail messages with English and German texts and an attachment. The attachment is a ZIP archive containing the worm's executable.
The worm composes messages with subject lines such as "I've_got your EMail on my_account!" and "FwD: Ich bin's nochmal" with attachments such as your_text.zip.
Installation to system
When the worm's file is started it opens text editor with the following text as a decoy:
When the worm's file is run, it copies itself as "services.exe" into the %WinDir%\Config\system\ folder, created by the worm.
Sober.N worm adds startup keys for "services.exe" in System Registry:
[HKLM\Software\Microsoft\Windows\CurrentVersion\Run] "SystemCheck" = "%WinDir%\Config\system\services.exe" [HKCU\Software\Microsoft\Windows\CurrentVersion\Run] "_SystemCheck" = "%WinDir%\Config\system\services.exe"
The worm also creates the following files to installation folder:
'zipped.wrm' contains base64-encoded worm, used in spreading. 'maddsys.xyz' is used to store email addresses.
The worm also writes the following files to system folder:
nonrunso.ber langeinf.lin adcmmmmq.hjg xcvfpokd.tqa
These files are used to deactivate previous variants of the worm.
Spreading in E-mails
The worm sends different types of e-mail messages with English and German texts and its file attached. The attachment is a ZIP archive containing the worm's executable.
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 phtm 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 worm ignores e-mail addresses that contain any of the following substrings:
@www @from. smtp- @smtp. ftp. .dial. .ppp. anyone @gmetref sql. someone nothing you@ user@ reciver@ somebody secure whatever@ whoever@ anywhere yourname mustermann@ mailer-daemon variabel noreply -dav law2 .qmail@ freeav @ca. abuse winrar domain. host. viren bitdefender spybot detection ewido. emsisoft linux @foo. winzip @example. bellcore. @arin @iana @avp icrosoft. @sophos @panda @kaspers free-av antivir virus verizon. @ikarus. @nai. @messagelab nlpmail01. clock
The worm composes e-mails with both English and German texts. If the worm sends infected messages to domains with suffixes '.de', '.ch', '.at', '.li' and also to 'gmx.' domain, it composes messages in German, otherwise English messages are composed.
The worm composes the following messages:
I've_got your EMail on my_account! FwD: Ich bin's nochmal
Hello, First, Very Sorry for my bad English. Someone is sending your private e-mails on my address. It's probably an e-mail provider error! At time, I've got over 10 mails on my account, but the recipient are you. I have copied all the mail text in the windows text-editor for you & zipped then. Make sure, that this mails don't come in my mail-box again. bye Verdammt,,,, ich hatte vergessen Dir meinen Text mitzuschicken. Aber bitte nicht woanders darueber Reden, ich wuerde mich dann zu Tode blamieren! Ich melde mich. Bis bald ;)
The actual worm executable name inside the attachement is 'mail.document.Datex-packed.exe'.
Sober.N worm is detected with the following FSAV updates:
Detection Type: PC
Description Created: Mikko Hypponen; April 19th, 2005
Technical Details: Jarkko Turkulainen; April 19th, 2005
Description Last Modified: Jarkko Turkulainen; April 20th, 2005