MI5's Andrew Parker warns that thousands of extremists in the United Kingdom see the British public as target for terrorist attacks. Threats to the British public are increasingly becoming more diverse, Parker said.
In his first public speech, Parker noted that being under the government's radar "does not necessarily mean being under our microscope."
Parker also noted that Al-Qaeda is an immediate threat to the country. He also warned of the "enormous" damage caused by a leak of GCHQ documents.
Mr Parker, who was in Whitehall to speak to the Royal United Services, added that security services in the UK should have access to numerous modes of communication that terrorists use.
Parker also revealed the frustrations and fears of the security service over technological advancements and those leaking the British government's secrets to the public domain.
Terrorist Attacks from 2000 to 2013
June 1, 2000 - An IRA bomb exploded on Hammersmith Bridge in London
September 20, 2000 - RPG was fired by the IRA at the MI6 HQ.
March 4, 2001 - Car bomb from Real IRA detonates just outside the main news centre of the BBC in London. An underground worker sustained eye injuries from flying glass.
April 16, 2001 - The IRA bombed Hendon post office.
May 6, 2001 - A bomb detonates at a postal sorting office in the British capital. One person sustained injuries.
August 3, 2001 - A bomb explodes in West London. Seven people were injured. The Real IRA claimed responsibility for the attack.
November 4, 2001 - A car bomb explodes in Birmingham.
July 7, 2005 - Bombings in London were perpetrated by four suicide bombers. Fifty-six people died and 700 were injured.
January to February 2007 - 2007 UK Letter Bombs
June 30, 2007 - Islamist extremists attacked Glasgow International Airport.
May 22, 2008 -An attempted suicide bombing was done by an Islamist extremist. He was the only one injured.
May 22, 2013 - A British serviceman was killed in the 2013 Woolwich attack. The Islamist perpetrators were armed with blades and a handgun.
To contact the editor, e-mail: