Security attacks by former employees that have been laid off will increase during the economic downturn, Microsoft has warned.

According to the tech giant, malicious insider breaches are on the rise this looks set to continue.

Doug Leland, general manager of Microsoft's Identity and Security department told the BBC: "This is one of the most significant threats companies face. With 1.5 million predicted job losses in the US alone, there's an increased risk and exposure to these attacks".

Visit Security Advisor for the latest internet threat news, FREE net threat email newsletters, and internet security products

Visit Broadband Advisor for the latest internet news, reviews, tips & tricks - and to take advantage of PC Advisor's unique, independent Broadband Speed Tester

"The malicious insider is classed as the greatest security concern because they have access, and relatively easy access, to corporate assets," said Leland.

According to Kevin Rowney from Symantec's Data Loss Prevention Unit, the culprits in most malicious insider attacks the culprits are acting in "revenge".

"We have even seen it as bad as people who got pink slips [redundancy notice], that day going to a customer data base and forwarding huge blocks of this data out the door so they can then set up shop and sell to the same customers the next day".

See also: BT and T-Mobile to safeguard sensitive data