As of September 15, 2003, Symantec Security Response downgraded the threat of this worm to a Category 2 from a Category 4. More formally known as W32.Sobig.F@mm, this was a mass-mailing worm that sent itself to all the email addresses found in the files with extensions dbx, .eml, .hlp, .html, .htm, .mht, .txt and .wab. The worm used its own SMTP engine to propagate, and though it tried to create a copy of itself on reachable and unprotected network drives, it failed to do so because it had glitches in the code. Symantec Security Response. W32.Sobig.F@mm. [Online, July 28, 2004.] Symantec Security Response Website. http://securityresponse.symantec.com/avcenter/ email@example.com.