Yet another virus is using E-mail to gain entry into business networks and infect computer systems. Today, a new Internet worm, I-Worm.ExploreZip, made its way into enterprise networks via an E-mail message with attached zipped documents.

Once the zipped file is opened, it looks as if it's running WinZip. What is actually happening is .zip attachments are expanding to overwrite operating-system components, apparently erasing files on the PC's hard drive. The worm looks through local and networked drives C to Z, searching for files with .h, .c, .cpp, .asm, .doc, .xls, and .ppt, and then erases them.

If a PC is infected, it will reply to every E-mail it receives, sending the virus back to the Internet. The reply E-mail reads:

"Hi [recipient's name]! I received your E-mail and I shall send you a reply ASAP. Till then, take a look at the attached zipped docs."

Several companies, including General Electric Co., reportedly shut down their E-mail systems today to cope with the worm virus.

Network Associates, Symantec, Trend Micro, and other antivirus software vendors are posting antidotes to the virus on their Web sites today.