1. A method for software code analysis, comprising: automatically normalizing a body of software source code by a computer, so as to generate a flow graph of the code, wherein the flow graph includes a sequence of tags representing instructions in the software code; applying a sequence mining method to the flow graph of the code in order to identify a group of a plurality of sub-sequences in the sequence of tags of the flow graph, which sub-sequences are similar to each other; determining for the identified group of sub-sequences, a common norm pattern; finding a sub-sequence within the group deviating from the common norm pattern, by an extent beyond a threshold; and reporting the deviating sub-sequence as a potential vulnerability in the software source code, wherein the tags in the sub-sequences have the same order as in the sequence, but adjacent tags in the sub-sequences are not necessarily adjacent in the sequence.