Network-based intrusion detection and prevention systems -NIDS /NIPS- have been widely implemented in order to build layered information security infrastructures. Many intrusion detection and prevention algorithms have been developed and its operation modes imply benefits and drawbacks that are not taken into account when choosing a network IDS/IPS. This paper assesses the network security provided by five NIDS/NIPS software solutions, by analyzing the protection against malicious traffic. Security platforms against network intrusion such as Snort Inline, Stonegate IPS, Strataguard, Intrupro and Packetalarm are tested and analyzed.