General Ali Mamluk, who was appointed on Tuesday as the new head of Syria's National Security office, is a career intelligence officer and a confidant of President Bashar al-Assad.
"General Ali Mamluk, who was head of state security, is becoming the head of the Bureau of National Security, with the rank of minister, overseeing the entire security apparatus," a security official told AFP in Damascus.
His appointment comes in a shake-up of the security services after a Damascus bombing on Wednesday killed four top regime figures including a brother-in-law of Assad.
Mamluk is a Sunni Muslim from Damascus, who has been a central figure of Syrian security for decades although most of the top echelons belong to the minority Alawite sect from which the Assads hail.
In his new role, Mamluk "will report directly to President Bashar al-Assad," the source told AFP.
Assad appointed him as head of the General Security Directorate in 2005, a position which he still holds.
Before that he was the second-in-command of the feared intelligence services of the Syrian Air Force.
Mamluk has been targeted by US and EU sanctions since mid-2011 and is accused of being responsible for human rights abuses.
As head of state security, he played an important role in repressing dissent.
Born in 1946, Mamluk has a grey moustache and is known to enjoy British cigarettes. He is married to a woman who hails from the central province of Homs, one of the first to rebel against the regime.
He used to head the anti-terrorist unit and have good ties with Western intelligence services at a time some years back when Syria tried to polish its image abroad.
A diplomatic cable published by WikiLeaks says that Mamluk had met US diplomats in 2010 to discuss ways of cooperating with Washington in the struggle against terrorism.
Another leaked US diplomatic cable dated 2007 speaks of Mamluk's "objectionable activities regarding Lebanon, and his suppressing Syrian civil society and the internal opposition."
Syria occupied Lebanon militarily and politically for nearly three decades until 2005, when its troops were forced to pull out of the country under international pressure.
Rami Abdel Rahman, director of the Britain-based Syrian Observatory for Human Rights, has described Mamluk as a contradictory figure who was involved in the brutal crackdown on dissent but who was also open to dialogue.
Mamluk has met frequently with opposition figures inside Syria after their release from jail "to incite them to renounce violence and back the reforms of the Assad regime," Abdel Rahman said.