Code clone detection is involved with detecting duplicated fragments of code within a code base. Detecting these clones is useful for maintenance operations which require editing the clones. The tools developed are expected to be robust enough to identify clones even when they have been modified, whilst preserving reasonable recall and precision rates. It is also expected that these tools be easily adaptable to different programming languages. The major approaches to this problem has involve the use of direct string matching, token comparison or comparison using abstract syntax trees. It is difficult to compare detection tools due to the absence of a standardized framework for measurement. More work should be done to make the existing tools useful for other practical/industrial purposes.