Hackers have managed to penetrate computer networks associated with the Israeli military in an espionage campaign that skillfully packages existing attack software with trick emails, according to security researchers at Blue Coat Systems Inc.

The 4-month-old effort, most likely by Arabic-speaking programmers, shows how the Middle East continues to be a hotbed for cyberespionage and how widely the ability to carry off such attacks has spread, the researchers said.

Waylon Grange, a researcher with Blue Coat who discovered the campaign, said the vast majority of the hackers' software was cobbled together from widely available tools, such as the remote-access Trojan called Poison Ivy.