Those photos of Jessica Alba may be murder on your PC. That Google search result that looks as if it answers all your questions may do nothing but create a serious tech headache. The fun you had watching that hilarious video you downloaded may not be worth the misery it can cause your system.
You've been warned that the Internet is something of a security minefield--that it's easy to get in trouble. You can do everything you can think of to protect yourself and still be taken by a malware infection, a phishing scam, or an invasion of online privacy. We'd like to provide a little help. Here are some of the hazards you may encounter, how dangerous they are, and what you can do to stay out of harm's way.
Slideshow: Quiz: Do You Know IT Security?
Not all Web dangers are created equal. Thankfully, our friends at the Department of Homeland Security have made our work of classifying Web threats a little easier. Will you get taken just by visiting that unfamiliar site? Or will you have to look for trouble? Let our threat level indicator be your guide.
Threat 1 >> Malicious Flash files that can infect your PC
The Place: Websites that use Flash
Adobe's Flash graphics software has become a big malware target in recent years, forcing the company to push out frequent security patches. But another danger you might not know about is associated with Flash cookies. Flash cookies are small bits of data that their creators can use to save Flash-related settings, among other things. But like regular cookies, Flash cookies can track the sites you visit, too. Worse still, when you delete your browser's cookies, Flash cookies get left behind.
If You Have to Go There: To help protect against Flash-based attacks, make sure you keep your Flash browser plug-ins up-to-date. And you can configure the Flash plug-in to ask you before it downloads any Flash cookies.
Threat 2 >> Shortened links that lead you to potentially harmful places
The Place: Twitter
Scammers love Twitter since it relies so much on URL shorteners, services that take long Internet addresses and replace them with something briefer.
And it's very simple to hide malware or scams behind shortened URLs. A shortened link that supposedly points to the latest Internet trend-du-jour may be a Trojan horse in disguise.
If You Have to Go There: Simply don't click links. Of course, that takes some of the fun out of Twitter. The other option is to use a Twitter client app. TweetDeck and Tweetie for Mac have preview features that let you see the full URL before you go to the site in question.
Threat 3 >> E-mail scams or attachments that get you to install malware or give up personal info
The Place: Your e-mail inbox
Although phishing and infected e-mail attachments are nothing new, the lures that cybercrooks use are constantly evolving, and in some cases they're becoming more difficult to distinguish from legitimate messages. My junk mailbox has a phishing e-mail that looks like a legitimate order confirmation from Amazon. The only hint that something's amiss is the sender's e-mail address.
If You Have to Go There: Don't trust anything in your inbox. Instead of clicking on links in a retailer's e-mail, go directly to the retailer's site.
Threat 4 >> Malware hiding in video, music, or software downloads
The Place: Torrent sites
Torrent sites (such as BitTorrent) are often used for sharing pirated music, videos, or software, and are a trove of malware. No one vets the download files--they may be malware in disguise.
Ben Edelman, privacy researcher and assistant professor at Harvard Business School, thinks torrent sites are the most dangerous places to visit, since they don't have a business model or reputation to defend (by comparison, many porn sites rely on being deemed trustworthy). "The [torrent] customers, they really don't want to pay," he says.
If You Have to Go There: It's probably best to avoid torrent sites entirely, given their untrustworthy content, but if you must visit, use a secondary PC to protect your main system. Use antivirus software, and keep it updated. Scan downloaded files and wait a couple of days before opening them. Brand-new malware can be tricky to catch, but the delay in opening may allow your antivirus software to get the necessary signatures.
Threat 5 >> Malware in photos or videos of scantily clad women
The Place: ‘Legitimate' porn sites
Porn sites have a reputation of being less secure than mainstream sites, but that assumption doesn't tell the whole story. "There is no doubt that visiting Websites of ill-repute is deadly dangerous. If you make a habit of it, it's a given that you'll be attacked at some point," says Roger Thompson, chief research officer with security firm AVG. "Unfortunately, staying away from those sites won't keep you safe by itself, because innocent sites get hacked all the time, and are used as lures to draw victims to the attack servers."
And as mentioned earlier, many porn sites operate as actual, legitimate businesses that want to attract and retain customers. That said, it may be hard to tell the "legit" porn sites from malware-hosting sites that use porn as a lure.
If You Have to Go There: Be suspicious of video downloads, or sites that require you to install video codecs to view videos (see the next threat, below). Using tools like AVG's LinkScanner and McAfee's SiteAdvisor can help you weed out the malicious sites.
And, again, consider visiting such sites on a secondary machine. You don't want your browser history on the family PC.
Threat 6 >> Trojan horses disguised as video codecs, infecting your PC with malware
The Place: Video download sites, peer-to-peer networks
If you watch or download video online, you've likely been told to download a video codec--a small piece of software that provides support for a type of video file--at least once. Usually, these bits of software are perfectly legitimate (for example, the popular DivX codec), but some less-than-reputable download services or video sites may direct you to download a piece of malware disguised as a codec. Security software company Trend Micro provides a good example of what these attacks look like.
If You Have to Go There: Your safest option is to stick with well-known video sites such as YouTube and Vimeo. And for catching up on the latest episodes of your favorite TV shows, sites and services like Hulu, TV.com, ABC.com, and iTunes are safer than peer-to-peer networks.
Threat 7 >> Geolocation--your smartphone and perhaps other parties know where you are
The Place: Your smartphone
The smartphone market is still in its infancy, really, and so are the threats. One possible concern is the use--or abuse--of geolocation. Although plenty of legitimate uses for location data exist, the potential for inappropriate uses also exists. In one case, a game listed on the Android Market was in reality a client for a spy app. In a less invidious example, a site called pleaserobme.com showed that--for a time--a stream of FourSquare check-ins indicated that a person was away from their home (the site's goal, mind you, wasn't to condone theft, but to raise awareness of the issue).
If You Have to Go There: Be particular about the location-based sites, apps, and services that you use. As shown in the screenshot at right services such as Yelp provide good examples of useful location-aware apps. On the other hand, weigh the privacy implications of services like FourSquare or the new Facebook Places feature, and consider how much you feel comfortable divulging. (Read more on how to retain privacy on FourSquare and Facebook Places.)
Threat 8 >> 'Poisoned' search engine results that go to malware-carrying Websites
The Place: Search engines
Search engine poisoning is the practice of building tainted sites or pages that are designed to rank high in a search on a given topic. For example, according to a recent study by the security firm McAfee, 19 percent of search results for "Cameron Diaz and screensavers" had some sort of malicious payload. Breaking news topics and Facebook are also common search targets for attackers.
If You Have to Go There: Pick and choose which sites to go to. Don't just blindly click search results; check each URL first to make sure that it really leads to the site you want. Although any site can be hacked, visiting the Washington Post's story on a hot news topic, for example, is probably a wiser choice than following a link to a site you've never heard of before.
Threat 9 >> Malicious PDFs that try to fool you into installing malware
The Place: Hacked Websites, plus your inbox
As Microsoft has become more serious about Windows security over the past few years, would-be attackers have had to find new ways to infect PCs. Attacking flaws in Adobe Acrobat is one of these newer methods. So-called poisoned PDFs are PDF files that have been crafted in such a manner that they trigger bugs in Adobe Reader and Adobe Acrobat; posted on a hijacked Website, they may let an attacker commandeer your PC and access your files and personal info.
A newer variant takes an otherwise innocent-looking PDF document and inserts malware into it. Adobe Reader may pop up an alert asking if you want to run the malware, but hackers can edit those messages to trick you into opening the file.
How serious is this problem? In 2009, attacks using malicious PDFs made up 49 percent of Web-based attacks, according to security firm Symantec.
If You Have to Go There: First, always make sure that you're running the latest version of Adobe Reader.
You can also use a different PDF reader, such as Foxit Reader. This can protect you from attacks on holes in Adobe Reader itself, but it won't make you immune to all PDF attacks, such as the newer ones that embed malware inside the PDFs. Make sure, also, that you update to Adobe Reader 9.3.3 or later (Reader 8 users should update to version 8.3.3 or later); these updates change the way Adobe Reader handles non-PDF attachments and reduce the risk from such attacks.
You can turn off Adobe Reader's ability to open non-PDF attachments by going to Preferences, clicking Trust Manager, and unchecking Allow opening of non-PDF file attachments with external applications.
The next major release of Acrobat and Reader will provide a new "protected mode" against these attacks.
Threat 10 >> Malicious video files using flaws in player software to hijack PCs
The Place: Video download sites
Attackers have been known to exploit flaws in video players such as QuickTime Player and use them to attack PCs. The threats are often "malformed" video files that, like malicious PDFs, trigger bugs in the player software that let the attackers in to spy on you, plant other malware, and more.
If You Have to Go There: Keep your player software up-to-date. Apple and Microsoft periodically release patches for QuickTime and Windows Media Player, respectively. Avoid downloading videos at random. Stick to well-known video sites such as YouTube, or to download services like iTunes.
Threat 11 >> Drive-by downloads that install malware when you visit a site
The Place: Hacked legitimate sites
A drive-by download occurs when a file downloads and/or installs to your PC without you realizing it. Such downloads can happen just about anywhere. Some sites are built to lure people into a drive-by download; but in a common attack method, criminals will hack a Web page, often on an otherwise legitimate site, and insert code that will download malware to your computer.
If You Have to Go There: The first thing to do is to keep your security software up-to-date, and to run regular malware scans. Many security suites can flag suspicious downloads.
Threat 12 >> Fake antivirus software that extorts money--and your credit card information
The Place: Your inbox, hacked legitimate sites
Fake antivirus programs look and act like the real thing, complete with alert messages. It isn't until you realize that these alerts are often riddled with typos that you know you're in trouble.
Most fake antivirus software is best described as extortionware: The trial version will nag you until you purchase the fake antivirus software-which usually does nothing to protect your PC. Once you send the criminals your credit card information, they can reuse it for other purposes, such as buying a high-priced item under your name.
You can get infected with a fake antivirus app in any number of ways. For example, in drive-by downloads (see the previous item), a malicious payload downloads and installs without the user realizing it or having any time to react.
If You Have to Go There: If you get an alert saying you're infected with malware, but it didn't come from the antivirus software you knowingly installed, stop what you're doing. Try booting into Safe Mode and running a scan using your legitimate antivirus software.