The 100 websites most affected by viruses each have about 18,000 nasties to attack net users' computers, an internet security company says.
Simply visiting one of the "Top 100 Dirtiest" websites - without downloading or even clicking anything - could expose your computer to infection and put your personal information into the hands of criminals, anti-virus software company Norton Symantec said.
Company spokeswoman Natalie Connor said the list was compiled using global data collected on Norton Safe Web, a site that analyses websites' security risks and has 20 million users providing site reviews.
The top 100 infected sites had on average 18,000 threats and 40 per cent of the sites had more than 20,000 threats.
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A staggering 75 per cent of websites on the list were found to be distributing "malware" for more than six months.
Malware is malicious software that can damage or compromise a computer system without the owner's consent.
Ms Connor said half of the websites on the list had adult content. Many have unprintable names indicating they contain hard-core pornography.
Others, not so easy to spot as crinminals' lures, include sites about ice-skating, deer-hunting, catering and legal services.
"What people don't realise is when you type in a website, you're bringing down information on a page and with it could be malware," she said.
Hackers could then obtain personal information using keystroke logging software maliciously installed on your computer.
Ms Connor said hackers were targeting vulnerabilities in website browsers and this affected both PCs and Mac computers.
"It's real," she said. "The last thing we want to do is scare people. We want to educate them so they know how to protect themselves."
Cyber criminals were becoming increasingly sophisticated and operating underground, Ms Connor said.
"It's not about the fame any more of creating viruses and getting in the media," she said. "They're making money."
Even if only 1 per cent of internet users fell for a scam and exposed their credit-card details, their losses could add up to millions of dollars, Ms Connor said.
Websites that made the list include:
* 17ebook.co
* aladel.net
* bpwhamburgorchardpark.org
* clicnews.com
* dfwdiesel.net
* divineenterprises.net
* fantasticfilms.ru
* gardensrestaurantandcatering.com
* ginedis.com
* gncr.org
* hdvideoforums.org
* hihanin.com
* kingfamilyphotoalbum.com
* likaraoke.com
* mactep.org
* magic4you.nu
* marbling.pe.kr
* nacjalneg.info
* pronline.ru
* purplehoodie.com
* qsng.cn
* seksburada.net
* sportsmansclub.net
* stock888.cn
* tathli.com
* teamclouds.com
* texaswhitetailfever.com
* wadefamilytree.org
* xnescat.info
* yt118.com
AAP