Several antivirus firms have spotted a new variant of the Sober worm in the wild, hiding in e-mails with English and German text.
According to Cupertino, Calif.-based Symantec, W32.Sober-J is a mass-mailer that uses its own SMTP engine to send itself to e-mail addresses it gathers from the computers it infects. "The subject of the e-mail varies and is in either English or German," the company said in its advisory. "The e-mail sender address is spoofed. The name of the e-mail attachment varies, and it has a .bat, .com, .pif, .scr or .zip file extension. The attachment may also have a double extension. This threat is written in the Microsoft Visual Basic programming language and is compressed with UPX."
Finnish security firm F-Secure Corp. said Sober-J was seeded in e-mails Jan. 31 and is "quite similar to the previous variants." While most AV companies consider it a low risk, Santa Clara, Calif.-based McAfee said it has seen enough activity to issue a medium-threat alert.
What it looks like
If the worm sends infected messages to domains with suffixes ".de," ".ch," or ".at," it composes a message in German. Otherwise, an English message is made.
In English, the subject line is: I've got YOUR email on my account!!
The body of the e-mail reads: "Hello, First, Sorry for my very bad English! Someone send your private mails on my email account! I think it's an Mail-Provider or SMTP error. Normally, I delete such emails immediately, but in the mail-text is a name & address. I think it's your name and address. The sender of this mails is in the text file, too. In the last 8 days i've got 7 mails in my mail-box, but the recipient are you, not me. Lol. OK, I've copied all email text in the Windows Text-Editor and i've zipped the text file with WinZip. Bye." The attached file is either "email_text.zip" or "text.zip."
E-mail addresses are harvested from files with the following extensions on the victim's machines: abc; abd; abx; adb; ade; adp; adr; asp; bak; bas; cfg; cgi; cls; cms; csv; ctl; dbx; dhtm; doc; dsp; dsw; eml; fdb; frm; hlp; imb; imh; imh; imm; inbox; ini; jsp; ldb; ldif; log; mbx; mda; mdb; mde; mdw; mdx; mht; mmf; msg; nab; nch; nfo; nsf; nws; ods; oft; php; phtm; pl; pmr; pp; ppt; pst; rtf; shtml; slk; sln; stm; tbb; txt; uin; vap; vbs; vcf; wab; wsh; xhtml; xls; and xml.