Methods for performing exact search string matches in the data plane of a network processor. The methods employ a two-stage string search mechanism to identify the existence of a search string from a set S in a packet payload. A first pre-processing stage identifies a potential search string match and a second analysis stage determines whether the first stage match corresponds to an exact string match. The first stage is implemented using hash values derived from at least one of search strings in set S or sub-strings of those search strings. In one embodiment, a plurality of Bloom filters are used to perform the first pre-processing stage, while in other embodiments various CAM-based technique are used. Various TCAM-based schemes are disclosed for performing the second analysis stage. The methods enable packet payloads to be searched for search strings at line-rate speeds.