The Research And Implementation Of Bridge-Firewall In Portable Storage Devices

With the rapid development of networks and communication technology, the Internet had exposed the vulnerability and was faced with enormous security threat. Network security technology had aroused great attention and became the current hot research issues. Firewall to protect internal network technology as an effective and traditional means had been widely used and continues to develop.This paper focused on the design and realization of a Linux-based software bridge-firewall system in the mobile storage devices, which is simple, flexible, efficient and can be rapid deployed. And the destination was to pay a minimum cost while protecting the internal network. The main research results are as follows:1. This paper longitudinally analysed and compared various ways of working behalf of the firewall, advantages and disadvantages. After having examined working behalf of the general firewall and bridge-firewall in detail, this paper summed up the advantages of bridge-firewall through horizontal comparison between the two on the impact to the network topology and the forwarding efficiency differences.2. From code-level this paper analysed the framework of the separate bridge module and the separate netfilter firewall module, the forwarding flow of packets in the bridge module as well as the filtering flow of IPv4 packets in the netfilter firewall module in detail. On this basis, this paper designed and implemented a method combining the bridge module and netfilter firewall module together to achieve a bridge-firewall core by changing the forwarding flow and the filtering flow of packets.3. This paper described the process of moving a Linux kernel with above bridge-firewall functionality to a Usb disk representing ordinary removable storage devices. After testing, we successfully built a Linux-based bridge-firewall system in the mobile storage devices, which is flexible, highly efficient and rapidly deployable.