The disclosure raises questions about the effectiveness of a wide range of networking security products, but experts say those kind of questions are nothing new. There is no evidence that the attack methodologies, made possible by an internally developed testing tool at Stonesoft, are being used in the wild. Security experts consulted by Threatpost noted that strategies for evading IDS and IPS are almost as old as the technology itself. ICSA Labs said vendors tend to focus on likely attack vectors, rather than feasible, but unlikely attacks.
Source: https://threatpost.com/warning-about-ids-evasion-greeted-chorus-meh-101910/74588/