IDS Evasion Techniques
Since the introduction of intrusion detection systems they became very popular amongst network administrators because it provided a way to detect if any attacks took place. At them days (1990s) these systems were very simple devises that monitor the network traffic, match it to a database of signatures and if there is a match an alert is produced that informs the administrator of the event
(Bruneau, 2001, History and Evolution of Intrusion Detection, p. 3). Throughout the years attackers, security professionals, researchers and developers have always played a cat and mouse game. Every time developers, security professionals and researchers find or develop new ways to counteract attacks, attackers seem to develop new ways to attack security devises such as IDSs or even bypass them altogether. This is because of the complexities in capturing, analysing and understanding network traffic (Timm, 2002, IDS Evasion Techniques and Tactics, p. 1). These complexities meant the existence of many techniques that can be used to take advantage of the weaknesses in IDSs. These methods were very simple such as pattern matching, denial of service (DOS) and false positives. However overtime more advanced techniques such as fragmentation, session splicing and polymorphic shell-code techniques began to appear.
As mentioned by (Roberts, 2010)
that stonesoft’s disclosure of a new way to evade IDSs and IPSs (IDPSs) raises some doubts about the effectiveness of many security products already used by many organisations worldwide. However stonesoft’s discovery was not new; anyone has an interest in information security knows that these techniques have been around for a very long time and was first mentioned in 1998 by (Newsham, 1998).
As quoted by (Roberts, 2010):
“Researchers working for Stonesoft have been delving into evasion techniques since 2007 in an effort to improve Stonesoft’s own products, said Matt McKinley, Director of Product Management in the U.S.”
He further quoted:
“”In the process of doing so, we basically discovered that it’s possible to combine multiple evasion techniques together working at different layers (of the IP stack) and they can confound the IPS and become hard to protect,” he said.”
However, I respectfully disagrees with what Mr. Matt McKinley had said; this is because these techniques as will be discussed in the following sections have been around for a very long time and all are based on the techniques mentioned in
In this section the author presents an overview of some of these techniques by dividing them into two categories Basic techniques and Complex techniques.