Worms are something everyone but birds and fishermen try to avoid. But when the term “worm” is used to describe something going haywire on the Internet, it can mean something almost inescapable could attack your personal computer.

During the past few weeks a computer virus dubbed “Blaster” and a computer worm named “Sobig” slowed or halted the operations of up to half a million computers worldwide. That sent information technology departments everywhere scrambling to find the appropriate “antibody.”

Sobig took advantage of a security flaw in Microsoft Windows operating system software, the most common operating system on the planet.

Jeff Wallace, a manager at WhidbeyNet — a subsidiary of Whidbey Telephone Co. — said his company has been working hard to stay ahead of the worm viruses.

“The traffic of these viruses has gone way up,” said Wallace.

But what are the worms?

According to the McAfee Security Web site, worms like Sobig aren’t quite a virus, but they are virulent. They are parasitic computer programs that replicate. But, unlike viruses, they don’t infect other computer program files. They copy themselves on the same computer, or can send the copies to other computers via a network.

Wallace said WhidbeyNet workers log how many viruses and worms they filter out before they have a chance to make their way to local homes and businesses. He said in the past three weeks, WhidbeyNet has gone from catching 700 per day to almost 30,000.

“It’s just unbelievable,” he said.

What makes the worms such a nuisance to computer users is that they duplicate and send copies of themselves to other computers via e-mail, Wallace explained. They come as an executable attachment, and they target machines with Microsoft Windows.

Macintosh computers tend not to be targeted by the creators of worms and viruses, since that operating system is installed on only a fraction of computers.

“I’m not aware of any of them that have affected a Macintosh,” said Wallace.

Just because an Internet provider can catch viruses and worms, computer owners shouldn’t let their guard down. They should still take measures to ensure they will stay virus- and worm-free. Of WhidbeyNet’s 9,000 customers, Wallace estimates approximately 100 have caught some type of virus or worm in the past few weeks.

Wallace suggests investing in virus filters and a firewall, which can prevent computers on a network from communicating directly with external computer systems. The software analyzes information passing between computers and rejects it if it does not meet pre-set rules.

“A firewall of some sort is a really good thing to do,” Wallace said.

McAfee and other protective systems also offer many tips on keeping a computer, whether in a home or office, free of viruses. One of McAfee’s tips is not to open any files attached to an e-mail from an unknown, suspicious or untrustworthy source, especially when the contents of an attachment are unknown.

Wallace said the worms can then replicate and spread themselves to other computers by using e-mail addresses on the user’s computer.

He also recommends that people update their anti-virus software on a regular basis.