Instead of clicking on the link, log-in directly to your social network and make sure the request is actually there, Marcus advised. If it is and you're still not sure you know the person, check out the person sending the request before you accept it.
4. Thieves Like Holiday E-Cards
They may be the environmentally-friendly option (and the more convenient one). But holiday e-cards are also a favorite among cyber thieves.
McAfee says it's discovered worms masquerading as Hallmark e-cards and corporate holiday promotions.
Instead of clicking on the link, open up a browser and enter the address yourself.
Or, if you don't know the person sending the e-card or it looks especially suspicious, Marcus said you're better of deleting it.
"If it was real, your friend will send it to you again," he said.
5. 'Luxury' Items Can Cost More Than You Think
If it looks too good to be true, maybe it just is. McAfee recently discovered a new scam that tricks shoppers into visiting malware-infected sites offering discounted luxury items from Cartier, Gucci and Tag Heuer.
Tech-savvy thieves even forge Better Business Bureau logos to convince shoppers of the sites' legitimacy.
If you want to buy a high-end item on end, type the company's address directly into your Web browser. And if you're looking for good holiday deals online, be sure to stick to respectable, well-known sites.
Marcus said you can still find deals with Google but recommended using safe-browser software that protects users from Web sites known to install malware.
6. Be Wary of Public Wi-Fi Hotspots
As you shop this holiday season, McAfee says to never shop online from a public computer or on an open Wi-Fi network.
There may be deals a plenty online but, if you're surfing the Internet on an open hotspot, hackers can spy on your activities and steal personal information as you enter it.
If you connect to a Wi-Fi network at the airport or at a hotel, Marcus said to be careful that you connect to the correct one. Look for signage on the wall directing you to the appropriate network and if you're not sure, ask someone.
7. 'Deck the Halls' Could Be Dangerous?
As you prepare to carol with friends and family, you might search the Web for Christmas carol lyrics. But McAfee says that hackers create holiday-themed Web sites for people hunting for festive ringtones, carols and screensavers.
Downloading infected files could install spyware, adware or other malware on your computer.
Before you start surfing, make sure you have comprehensive and up-to-date computer security software on your computer. And, as you search, steer clear of links with misspellings and other errors.
8. Steer Clear of Job-Related E-Mail Scams
The holidays are an expensive time and, if you're out of work, they can be extra stressful.
But don't fall victim to scams targeting job-seekers with work-from-home opportunities and promises of high-paying jobs.
In these scams, McAfee says, once the job-seeker sends his information and pays the "set-up" fee, off the hackers go with their money.
9. Auction Sites Fraught With Fraud
Auction sites can help you find good deals as you do your holiday shopping. But as you visit sites, make sure you actually land on eBay or Craiglist and not imposter sites, Marcus said.
And, as you place your bids, be careful about deals that look just a bit too sweet, as they probably are.