A system for preventing successful denial of service attacks comprises a first communication device, a second communication device, and a network. The first and second communication devices establish a communication session via the network. Based on various information, such as a pre-shared secret, one of the communication devices determines a network access filter value and compares this value to at least one data frame in order to authenticate such data frame without committing significant computing resource and any memory space. By updating the network access filter over time, an unauthorized user who discovers the outdated network access filter values is prevented from successfully launching a denial of service attack.