09-07-2013 02:37 PM
Cyber-thieves are behind a big leap in the number of computers connecting to the Tor anonymous web browsing system, a security company has said.
The number of connections to Tor almost doubled in late August.
Some thought the rise was caused by people in repressive regimes using Tor to escape official scrutiny.
But Dutch security company Fox-IT said it had evidence it had been caused by cybercriminals using Tor to control legions of hijacked home PCs.
The sharp leap in Tor numbers began on 19 August.
Before that date about 500,000 connections a day were being made to the network.
Within a week, the number of connections had hit 1.5 million and has continued to grow.
The latest update from Tor suggests about three million connections are now being made on a daily basis.
Tor (The Onion Router) attempts to hide who is using the web by routing their data through a series of computers each one of which encrypts the data passing through it.
It is widely used by people living in nations that monitor what citizens say online, to avoid official attention.
Many people on the Tor admin mailing list suggested the growth in use had been caused by more people turning to the network as many different governments cracked down on what can be said and done online.
But Fox-IT said it had traced the growing number of connections to a botnet - a network of home computers hijacked by malicious computer programs.
Botnets are the favoured tools of cybercriminals, who use them as a resource to plunder for saleable information or as a way to send spam or launch attacks on other sites.