A recent report by Akamai Technologies shows hackers are attacking corporate servers over mobile networks.
The report covers the third quarter of 2010, and shows the increasing use of the Telnet remote access protocol by hackers. Telnet has been gradually replaced by SSH, also known as Secure Shell.
Ten percent of attacks devoted to mobile networks came from Port 23, which is used by Telnet. Telnet accounted for about 17 percent of all attacks.
The attacks originated from mobile networks, but mobile devices did not appear to be the source.
"As noted previously, we believe that the observed attack traffic that is originating from known mobile networks is likely being generated by infected PC-type clients connecting to wireless networks through mobile broadband technologies and not by infected smartphones or similar mobile devices," according to the report.
The Akamai report includes information from more than 530 million unique IP addresses from more than 230 countries and regions. Much of the attack traffic from Port 445 occurred in Brazil, Germany, Russia, Taiwan and the United States, while China runs on Port 22, and saw attacks more common than Port 445.