Israeli security firm Blue Security has announced that it will discontinue its anti-spam service following a series of denial of service attacks that have devastated its business.

The company was hit by attacks from Russian spammer 'PharmaMaster' after Blue Security blocked the marketer's messages and sent them back to the machines from which they originated.

Blue Security had recently been awarded $4.8m in funding but its founder, Eran Reshaf, said the company did not have the resources to fight back against the spammer.

"This is something that's really got to be left to governments to decide because to fight the spammers you really need to spend $100m," Reshef told The Guardian.

"It's a dirty little secret that there is no real way to totally prevent denial of service attacks. If the attacker is prepared to put enough money in, then they can beat you every time."