Months before the attack in Benghazi took place, a State Dept report praised security at the consulate.
The report shows that while the revolution surrounding the ousting of Muammar Gaddafi was still raging, diplomatic security forces went to Benghazi to find a safe place where diplomatic personnel could live and conduct their business. At that time they found "a villa compound" they believed "significantly enhanced the security of all U.S. personnel in [Benghazi]."
On September 11, 2012, Ambassador Christopher Stevens was killed inside one of the buildings in the villa compound.
It's become common knowledge that Stevens knew the security was not sufficient, and asked for more. Security officers in Libya put in requests for more security for the compound as well.
The Obama administration ignored, and in some cases refused, the requests.