NSA's notorious global web surveillance scandal is being used by crooks to falsely accuse users of downloading illegal material, telling them their PCs are now locked from use, and ordered to hand over a cash "fine" to unlock their computers.

As has been the usual case, victims are told that their computer is infected and directed to download bogus AV software or in some cases, they are confronted with a bogus NSA warning that there is child porn on their computers and to hand over sums of money.

Cloud security firm Zscaler has spotted 20 hijacked domains hosting malicious web pages.

In the case of the child porn scareware, victims are told to hand over $300 to avoid prosecution.

"The attacker uses the recent news about PRISM to claim that the victim's computer has been blocked because it accessed illegal pornographic content," a blog post by Zscaler ThreatLabZ researcher Julien Sobrier explains.

"The victim has to pay $300 through MoneyPak, a prepaid card service."

"The ThreatLabZ team expect attackers to take advantages of the upcoming UK laws on accessing adult content online to send new types of fake warnings to UK victims."