Facebook Home Invasion

You've seen it before: A Facebook friend posts a link to a video that promises, "OMG! You won't believe what happened!" or an update warning you that Facebook will start charging users. You know that some posts are scams, but others seem legitimate. How do you know whether to click?

Graham Cluley, an independent security expert and former consultant at security firm Sophos, says that the rise of social networks has made it easy for scammers to take advantage of unsuspecting users.

"Before social networking, you had to consciously forward an email with malicious content to members of your address book," Cluley said. "But now with Facebook, it's just too easy to pass something along. You can click a link, 'like' a post or reshare something without thinking about the consequences. Before you know it, you've contributed to the problem and worsened the signal-to-noise ratio on the social network."

[ Android user? Watch out for scam apps. Read Scam Android Apps Plague Google Play. ]

Spotting Facebook scams can be easy if you know what to look for. Here are four common characteristics found in malicious posts, plus tips for how you can ensure you don't fall prey.

1. The Content Is Salacious

If a questionable post includes a level of shock, horror or salaciousness, be wary, Cluley said. You'll often find these types of posts promising a peek into celebrity sex tape or a video of something gruesome.

This type of content can disguise a clickjacking attempt, malware or phishing scheme. Pay particular attention to the language used and whether it's enticing you to click or take immediate action, Cluely said.

One recent scam preyed on actor Emma Watson, who starred as Hermione Granger in the Harry Potter movies. The Facebook post promises a clip of the actor in a leaked sex tape, and requests that you enter your information for "age verification," in addition to copying and pasting a script into your browser's address bar.

2. It Requires Extra Steps To View

Survey scams, which are popular on Facebook, ask you to complete a questionnaire in order to receive a prize, such as an iPad, or view a video, for example. These scammers make money by driving traffic to particular sites, Cluley says.

One recent example preyed on Costco customers. A widely circulated post read, "Claim your Free $500 Costco Voucher Now. Only a few left." Clicking on the post asked you to share the "offer," post something nice about Costco and like a Facebook page.

But Costco wasn't behind the bogus Facebook page -- scammers were, hoping to direct you to websites hosting surveys, earning them commission.

"Look at the content of the message and ask, 'What am I going to get from this?'" Cluley said. "If it asks you to install software or take a survey or reshare a message before you've seen what you expect to see, that's when an alarm bell should ring." 3. The Content Is Newsworthy But Promises Something Extraordinary

Facebook scammers often take advantage of popular, tragic or unexpected news, such as the death of a celebrity. These posts might promise the final pictures of the celebrity's life or the first pictures of their deceased body, Cluley said.

"Many of us are consumed by tabloid news and just out of morbid curiosity might be tempted to do what a post asks in order to view that video or photograph," he said. "It's understandable, too, because so much news breaks on social media."

These types of scams are often clickjacking attempts in which you see a thumbnail with the "Play" button. When you click it, you're actually clicking an invisible Like button. Your Facebook friends then see that you've liked that page or video and might like it themselves, further spreading the scam.

If you're tempted to click, Cluley said to ask yourself whether or not it's out of character for your friend to share such a video or image. If you're still unsure, Google the news in question or turn to a reputable news site for the content.

4. It Promises Something Facebook Would Never Do

Some of the most popular scams are those that ask you to download an app that shows you who has viewed your profile, Cluley said.

"These scams offer something every Facebook user wants, and it's something that is within Facebook's technical power to deliver," he said. "But Facebook is not going to do it, and they have no plans to do it. But people still click and before you know it, that message is spreading again."

Scammers also prey on newsworthy changes Facebook makes, such as announcing a new feature or privacy change, he said. One example of this is the "Graphic App" privacy warning hoax, in which users share a message warning of a change in Facebook's privacy settings. The message inaccurately warns of the privacy implications of Facebook's Graph Search, which recently rolled out to all users.

Before you share such a warning or sign an alleged petition to prevent Facebook from making a change, do your homework and verify the rumor or news, he said.

In addition, there are preventative measures you can take to ensure you stay safe while using Facebook.

Cluley advises that you:

-- Keep your antivirus software, plugins and patches current. Check regularly for updates.

-- Set a strong Facebook password that's difficult to guess and is one you're not using elsewhere.

-- Check to see which Facebook apps you've granted permission to and remove suspicious apps you don't remember downloading.