Here is something that I learnt to penetrate the Web Filtering.
The scenario here is I want to transfer binary files to an inside station that only have port 80 access. However, the port 80 is guarded by Web Filtering that restricted the file type to text only.
The filtering is not easy to be fooled; simply change the file name to .txt is not able to cheat the filtering. So the file has to be really a text file.
So here comes the solution.
The original idea is to use Binary to Text (exe2hex.exe) tool to transform the binary file to text (Hex). And then use the build-in windows tool “debug” to transform it back to binary.
However, there is a limitation; the debug is limited to work with only 64k bytes. The file size larger than that is not working. Use RAR to create the split binary files is a way to come over this problem. But, it’s just too trivial to split the file to many small binary files and then use Binary to Text (exe2hex.exe) to transform and then downloaded by the station.
So another tool comes to help.
Base64.exe could encode the binary files and then decode it back to binary. The size of the Base64.exe is less then 64k bytes, so we can use Binary to Text tool to transform it to text and use debug to reassemble it back.
Below is the reference websites:
Binary to Text (exe2hex.exe):
http://www.g615.co.uk/riftor/exe2hex.shtml
Base64.exe
http://www.rtner.de/software/base64.html
Thanks Master Min to share the expertise on this :)
