OpenRCE: Blog

DeleteFiber AntiDebug

Wed, 15 Aug 2007 04:24:35 -0500

I was reversing a piece of malware today when its decryptor revelead a trick i haven't seen before.

The trick seems to be based on the behaviour of DeleteFiber under debugger.

After calling it with an invalid parameter, it checks last set error using GetLastError which is
- 0x00000057 if process was not debugged
- other if process was under debugger

In the malware i was analysing the return value was used to build a jump to another section of the decryptor.

Easy code to conduct your own reversing.



char lama[1024]={0};

int main(int argc, CHAR* argv[])

{

        DeleteFiber(lama);

        printf("GetLastError = %.8x", GetLastError());

        return 0;

}

CommentViewer v.0.2 SRC

Mon, 05 Feb 2007 16:35:59 -0600

Thinking that Comments Viewer is a pretty decent plug-in for IDA and not much can't be added without losing focus on its main purpose, i decided to release its NOT SO NICE source code. Improvements are very welcomed, so don't be shy

Regards,

bLaCk-eye

DOWNLOAD SOURCE

Comment Viewer v0.2 plug-in

Sun, 05 Nov 2006 10:08:05 -0600

This is my first post on this website so please bare with me and my..let's say lack of knowledge.

Recently i have been doing some serious(or so i like to think) viral research and i was faced with a kind of nasty problem which i think most of you came across while doing advanced binary analysis. IDA allows users to comment parts of the database of the target the are studying to put notes and varios information to help them have a bigger picture of what is happening the huge sea of code. What amazes me is that IDA doesn't have a comment manager so you can see your comments, sort them , search inside them to find something you are looking for. This is no problem when reversing consists of a few quick looks over the target to figure out a particular method employed, but when we talk about binary audit or viral analisys and description things get a little complicated.

This is why i create a small plugin for ida which does just that: its a comment manager with a few extra options which i think should prove to be usefull from time to time.

No source code release at this time as it's still kind of a release candidate :).But source will be available soon.

Please check it out and let me know what you think about it, if you find it useful or just plain junk.

Link:
http://reteam.org/tools/tf29.zip

Regards,

bLaCk-eye