Before Season 1
Arvin Sloane sold a nuclear bomb to Hassan after Sydney uncovered it from the grave of Milovich Ivanov. Syndey learnt of this and went to Egypt to try to retrieve the bomb, but just as she found it she was confronted by Hassan himself (So It Begins).
Sydney tried to bargain with Hassan but he refused to take his gun off her. In retaliation, she threw the bomb, a small ball of plutonium that would kill them both within 48 hours, into the air. In the time it took for it to drop she managed to disarm Hassan then catch it again, before escaping (Parity).
Hassan stayed off the grid for quite some time until he sent a small team to rob a bank. The bank robbers stole a large sum of cash, as well as valuable assets that were frozen by the U.S. government (Mea Culpa).
Shortly after SD-6 discovered Hassan's offshore bank account number, they found out that he was selling arms to K-Directorate. Sydney was sent to Semba Island to see if she could locate Hassan there through a forager named Severn Driscoll. While there, she not only discovered Hassan's new name, Nebseni Sahd, but found out that Hassan had gone through plastic surgery and was living a secret life in Havana, Cuba. Upset over Hassan stealing from SD-6, Sloane sent Jack Bristow to Cuba to kill him. At the same time, Vaughn told Sydney that the CIA needs him alive (Spirit).
While in Cuba, both Jack and Sydney are captured by Hassan's men. Jack tries to lie his way out of the situation, at which point Hassan demands that Jack kill Sydney (Spirit). Sydney and Jack kill or knock out Hassan's men and take him hostage. Jack fakes Hassan's death before knocking him out so the CIA can take him to a safehouse in Los Angeles. The CIA demanded for Hassan to tell them about a package they were looking for, but Hassan refused to tell anyone what it was until his wife and son were safe (Confession).
Later on, after the CIA discovered Hassan's stockpile of weapons in Crete, Hassan led Sydney into a trap. Determined to get his deal, he intentionally told her the wrong code to enter the bunker, which triggered a device that filled the room with gasoline. Hassan informed Vaughn and other CIA agents that if he didn't get a signed document saying that his wife and son would also be put in protective custody, the room would ignite in sixty seconds, and Sydney would die. CIA Director Devlin just barely managed to get the document signed, and Hassan told the agents to code to deactivate the trap (Confession).
It can be assumed that Hassan and his family were put in protective custody immediately after Sydney retrieved the package.