A little networking humor. Excerpt:
4. Processing of the Evil Bit Devices such as firewalls MUST drop all inbound packets that have the evil bit set. Packets with the evil bit off MUST NOT be dropped. Dropped packets SHOULD be noted in the appropriate MIB variable. Intrusion detection systems (IDSs) have a harder problem. Because of their known propensity for false negatives and false positives, IDSs MUST apply a probabilistic correction factor when evaluating the evil bit. If the evil bit is set, a suitable random number generator [RFC1750] must be consulted to determine if the attempt should be logged. Similarly, if the bit is off, another random number generator must be consulted to determine if it should be logged despite the setting. The default probabilities for these tests depends on the type of IDS. Thus, a signature-based IDS would have a low false positive value but a high false negative value. A suitable administrative interface MUST be provided to permit operators to reset these values.