Most NIDS systems operate in layer 2 of the OSI model. These systems feed raw traffic into a detection engine and rely on the pattern matching and/or statistical analysis to determine what is malicious. Packets are not processed by the host’s TCP/IP stack allowing the NIDS to analyze traffic the host would otherwise discard. Which of the following tools allows an attacker to intentionally craft packets to confuse pattern-matching NIDS systems, while still being correctly assembled by the host TCP/IP stack to render the attack payload?