Abstract: With the theories of complex network, the paper researched error and attack tolerance of reply network on the Bulletin Board System. Firstly, the authors proposed five methods based on the degree and betweenness of nodes, in- eluding failure and attacks, and described the construction model of random network, scalcfrec network and reply net- work on I3I3S. Then, the definition and measure of error and attack tolerance were presented. Finally, the authors at- tacked networks with five methods. The results show that attacks can breakdown the network in seconds,while failure has little influence on networks, especially the reply network on BI3S, which means the reply network owned weaker at- tack tolerance and stronger error tolerance. Aimed to reduce the damage by attacked, we must protect the important nodes in the network, which have strong practical significance.

Key words: BBS network, Error and attack tolerance, Complex network