Holding a phone conversation with Sara Yanari is like talking with Sgt. Joe Friday of "Dragnet." A Geek Squad mission specialist out of Richfield, Minn., Ms. Yanari speaks in antiseptic terms that would make Jack Webb proud. And she never goes out of character, even if I try to lighten the subject with seemingly humorous remarks.

Ms. Yanari, and two other mission specialists, are ready to help the more than 12,000 Geek Squad agents who fan out around the country to help consumers tackle their computer problems.

It sounds like a large job -- especially when Cyber Monday comes around. That's the day that thousands of holiday shoppers go online after Thanksgiving to buy their holiday gifts. During the past decade, it has become a tradition, almost as ubiquitous as shopping at your favorite retail store on the day after Thanksgiving. Cyber Monday helps kicks off a holiday shopping spree that JupiterResearch expects to reach $39 billion transacted by 126 million online shoppers.

Although shopping by computer (or cell phone) has become habit, it unfortunately is still not as safe as it should be -- because scoundrels are waiting to prey on innocent shoppers who take nonsafe actions.

The first rule in safely shopping online is to shop in online storefronts that you know or that have been recommended by people you trust. Going into an unfamiliar Web site and giving your credit card information increases your chances of falling for a credit card thief or even an ID scam. If you're looking for Macy's, and your address bar says www.joesgarage.com/macys, you can bet that you're in the wrong store. So make sure you type the right characters too.

There are a number of ways that shopping online can be dangerous. Geek Squad has issued its list of Top 5 Security Threats, most of which can be attributed in part to online shopping:

1. Ransomware. This is where a malicious software designer hijacks your files, encrypts them so you can't get to them, and then demands payment from you before he'll release them to you. And you thought Bill Gates was the only techie that needed to worry about ransom.

2. ECard Scams. This is where somebody tricks you into visiting a malicious Web site by sending you what looks to be a greeting card by e-mail. It's not what it looks like.

3. Phishing/Vishing scams. In December, 24,000 people reported incidents to the Federal Trade Commission that involved a Web site trying to trick them into giving up credit card data voluntarily.

4. Pharming. This fairly new technique involves getting into your wireless home router, changing key settings and setting up false Web sites or pharms that you think are safe, and which collect key information from you.

5. Virtual keypads. You use these to type onscreen instead of on your keyboard. According to Geek Squad, virtual keypads don't protect you from people who monitor your keystrokes, even though some people think it does. Ms. Yanari cautions that key logging software is becoming particularly sophisticated and difficult to remove.

The common theme in dealing with these threats is to make sure you back up your data often and keep both anti-virus and anti-spyware current on your computers. Most importantly, be vigilant when you give out your credit card data to make sure you give it somebody you trust. It's easy to get swayed by a bargain from that unknown Web site. But don't. Check out the Web site first; then if it gets a seal of approval by BBB, the FTC or someone you know, buy confidently.