STATL An Attack Language for State based Intrusion Detection.
You can download it from the following link: https://packetstormsecurity.com/files/download/51926/STATL-An-Attack-Language-for-State-based-ID.pdf
Source: https://packetstormsecurity.com/files/51926/STATL-An-Attack-Language-for-State-based-ID.pdf.html