Al-Qaeda sympathisers have been trying to infiltrate the British security service MI5. But those with al-Qaeda sympathies had been weeded out during a six- to eight- month vetting process, officials added. The Security Service now publicly advertises for staff as part of a major expansion plan to combat terrorism, ending decades of secrecy. Tens of thousands apply to join MI5 each year, with 400 making it through to final selection. Applicants are first assessed by an outside agency, then those shortlisted invited to MI5's London headquarters, where their backgrounds and sympathies are intensively investigated for six to eight months. I know what they mean by length. I was succesful in an interview with GCHQ at their London Office in the late 90's. The developed vetting took so fecking long I ended up puling out and accepted a job with better pay.