Directory traversal is a form of HTTP exploit in which a hacker uses the software on a Web server to access data in a directory other than the server's root directory. If the attempt is successful, the hacker can view restricted files or even execute commands on the server. Directory traversal attacks are commonly performed using Web browsers. Any server in which input data from Web browsers is not validated is vulnerable to this type of attack.
Although some educated guesswork is involved in finding paths to restricted files on a Web server, a skilled hacker can easily carry out this type of attack on an inadequately protected server by searching through the directory tree. The risk of such attacks can be minimized by careful Web server programming, the installation of software updates and patches, filtering of input from browsers, and the use of vulnerability scanners.
Directory traversal is also known as directory climbing or backtracking.