The UK government is looking to recruit approximately 1000 new members of staff for the MI5. Grounded in 1909, MI5 was originally set up to tackle the German spy threat against the British navy.
The existence of MI5 was kept secret for a long time, but now has it's own website, http://www.mi5.gov.uk,, where it openly advertises for new members.
MI5's numbers are to increase to approximately 3000 to deal with the threat from al-Qaeda and other militant organisations. Source