ABSTRACT

The exploitation of the computer network security systems, especially through the vulnerability of format string of  Linux wu-ftpd 2.*, has become an interesting topic since it was found by security.is in June 1999. The problem emerging in this computer network system was considered the negative effect of the existence of open source application for server system which could be obtained in free of charge.
A bunch of people known as crakers, might have a thorough and deep knowledge of computer system security. This skill, combined with good mastery of operating system, capability of programming in C and elaborateness in reading source code, RFC, documents, and articles enables them to breach into a security system. A computer network system which has high risk factor and high level of threat as an effect of system compromise must be handled and managed in a special way. Having good understanding of buffer overflows technique and format string vulnerability, a cracker can get into the computer system.
Computer Incident Advisory Capability (CIAC) on June 26, 2000, at 17:00 GMT, in one of its information bulletin K-054 wrote about "Vulnerability in Linux wu-ftpd". It discusses the vulnerability of "SITE EXEC" command option of Linux wu-ftpd version 2.6.0 and of its predecessor. Analysis of the security system exploitation program through vulnerability is selected as the topics of this thesis. The supporting materials include articles and papers on CERT, CIAC, HERT, TESO and other textbooks related to memory process. Basically, there are two common things among exploitations of computer system: the use of the state of buffer overflows and the existence of format string vulnerability. The difference lies on the steps to take depending on the entrance gate selected (port and service).

Keywords :
      exploitation - buffer overflows - vulnerability -  format string - analysis