The right tools and a healthy level of suspicion can go a long way in keeping you safe online.

The Web is a fount of information, a busy marketplace, a thriving social scene — and a den of criminal activity.

Criminals have found abundant opportunities to undertake stealthy attacks on ordinary Web users that can be hard to stop, experts say. Hackers are lacing websites — often legitimate ones — with so-called malware, which can silently infiltrate visiting PCs to steal sensitive personal information and then turn the computers into “zombies” that can be used to spew spam and more malware onto the Internet.

At one time, virus attacks were obvious to users, said Alan Paller, director of research at the SANS Institute, a training organisation for computer security professionals. He explained that now, the attacks were more silent. “Now it's much, much easier infecting trusted websites,” he said, “and getting your zombies that way”.

And there are myriad lures aimed at conning people into installing nefarious programmes, buying fake antivirus software or turning over personal information that can be used in identity fraud.

“The Web opened up a lot more opportunities for attacking” computer users and making money, said Maxim Weinstein, executive director of StopBadware, a non-profit consumer advocacy group, which receives funding from Google, PayPal and Mozilla among others.

Google says its automated scans of the Internet recently turned up malware on roughly 300,000 websites, double the number it recorded two years ago. Each site can contain many infected pages. Meanwhile, malware doubled last year, to 240 million unique attacks, according to Symantec, a maker of security software. And that does not count the scourge of fake antivirus software and other scams.

So it is more important than ever to protect yourself and others from attackers. Here are some basic tips for thwarting them.

Protect the browser

The most direct line of attack is the browser, said Vincent Weafer, vice-president of Symantec Security Response. Online criminals can use programming flaws in browsers to get malware onto PCs in “drive-by” downloads without users ever noticing.

Internet Explorer and Firefox are the most targeted browsers because they are the most popular. If you use current versions, and download security updates as they become available, you can surf safely. But there can still be exposure between when a vulnerability is discovered and an update becomes available, so you will need up-to-date security software as well to try to block any attacks that may emerge, especially if you have a Windows PC.

It can help to use a more obscure browser like Chrome from Google, which also happens to be the newest browser on the market and, as such, includes some security advances that make attacks more difficult.

Get Adobe updates

Most consumers are familiar with Adobe Reader, for PDF files, and Adobe's Flash Player. In the last year, a virtual epidemic of attacks has exploited their flaws; almost half of all attacks now come hidden in PDF files, Mr. Weafer said. “No matter what browser you're using,” he said, “you're using the PDF Reader, you're using the Adobe Flash Player.”

Part of the problem is that many computers run old, vulnerable versions. But as of April, it has become easier to get automatic updates from Adobe, if you follow certain steps.

Adobe said it did not make silent automatic updates available previously because many users, especially at companies, were averse to them.

To get the latest version of Flash Player, visit Abobe's website.

Beware malicious ads

An increasingly popular way to get attacks onto websites people trust is to slip them into advertisements, usually by duping small-time ad networks. Malvertising, as this practice is known, can exploit software vulnerabilities or dispatch deceptive pop-up messages.

A particularly popular swindle involves an alert that a virus was found on the computer, followed by urgent messages to buy software to remove it. Of course, there is no virus and the security software, known as scareware, is fake. It is a ploy to get credit card numbers and $40 or $50. Scareware accounts for half of all malware delivered in ads, up fivefold from a year ago, Google said.

Closing the pop-up or killing the browser will usually end the episode. But if you encounter this scam, check your PC with trusted security software or Microsoft's free Malicious Software Removal Tool. If you have picked up something nasty, you are in good company; Microsoft cleaned scareware from 7.8 million computers in the second half of 2009, up 47 per cent from the 5.3 million in the first half, the company said.

Poisoned search results

Online criminals are also trying to manipulate search engines into placing malicious sites toward the top of results pages for popular keywords. According to a recent Google study, 60 per cent of malicious sites that embed hot keywords try to distribute scareware to the computers of visitors.

Google and competing search engines like Microsoft's Bing are working to detect malicious sites and remove them from their indexes. Free tools like McAfee's SiteAdvisor and the Firefox add-on Web of Trust can also help warn about potentially dangerous links.

Anti-social media

Attackers also use e-mail, instant messaging, blog comments and social networks like Facebook and Twitter to induce people to visit their sites.

It is best to accept “friend” requests only from people you know, and to guard your passwords. Phishers are trying to filch log-in information so they can infiltrate accounts, impersonate you to try to scam others out of money and gather personal information about you and your friends.

Also beware the Koobface worm, variants of which have been taking aim at users of Facebook and other social sites for more than a year. It typically promises a video of some kind and asks you to download a fake multimedia-player codec to view the video. If you do so, your PC is infected with malware that turns it into a zombie (making it part of a botnet, or group of computers, that can spew spam and malware across the Internet), exposes your personal information and possibly imperils your friends.

Spam filters and current security software can help protect you. Defensioa tool from Websense that is free, can block spam and malicious links from being posted on your blog or Facebook page.

But most important, you need to keep your wits about you. Criminals are using increasingly sophisticated ploys, and your best defence on the Web may be a healthy level of suspicion. — New York Times News Service