Skip to main content

Part 2 - Packing a RAT with UPX/Packers

Typically after a malware developer has created his malicious payload (for example using the steps mentioned in the post about generating a RAT with MSFVenom) they test whether that malicious program can be detected by antivirus software. 

Enter Virustotal. This is a website that can be used for both positive and negative means (as is the case with all forms of education). With Virustotal, bad actors can use it to test their payloads to see if it can be detected by antivirus software that is the most popular on the market. Regular actors/uses can use it to check if a tool or software they want to run on their computer is malicious or not.

How to do this is also illustrated in the video below. In most cases malware analysts use it for static analysis of potentially malicious programs. 

So typically there are a number of ways that antivirus software works but the one method that bad actors try to combat in this scenario is signature based analysis. By this, a hash is generated for each and every program that is scanned by antivirus software and then blacklists are generated from this. The blacklist is comprised of programs that are seen to be malicious. This hash is the signature of the malicious program.

So whenever we upload a program to Virustotal, the signature is generated and compared to the database of blacklisted malicious programs from a multitude of antivirus software.

Packing/Executable Compression/ Obfuscation is one way of avoiding this. In the most lay of layman terms, its basically sticking the malware in a shell and then passing that shell to the antivirus. The antivirus generates a hash of the shell and this is nothing like the signature of the malware contained within the shell and in most cases, a false-negative is the result. There are open-source packers like UPX and then there are others that are proprietary.

This demo shows how to pack and unpack a program using UPX.

This video tutorial is for educational purposes only.



Comments

Post a Comment

Popular posts from this blog

Password Cracking: RainbowCrack table generation, sorting and usage

I had to do this demo after one of my students asked for my assistance regarding how to use this tool. Usually, I just assign different tools to them individually depending on the aspect of penetration testing we are covering (session hijacking, vulnerability scanning, etc) and then tell them to submit a report and a video demo of how the tool is used. Anyway, after a brief one-to-one discussion I realized the student had actually done the research on how rainbow tables operate (above and beyond the material in the lecture slides) so I figured that if he was here asking for assistance, he genuinely needed it. The tool is available at the RainbowCrack site.  A detailed description of this nifty tool can also be found here . So, firstly I had to generate the rainbow tables. The command line syntax is: rtgen hash_algorithm charset plaintext_len_min plaintext_len_max table_index chain_len chain_num part_index where: hash_algorithm  Rainbow table is hash algorithm specific. R
Post a Comment
Read more

Malware Analysis: A Python Malware on campus 1

So a few weeks back after a class I'd taken with them,  a number of my students told me of a particular malware that was affecting students' computers, in particular, computers running Windows OS. According to them, if you tried to open a folder that was residing on the USB stick with the malware, the malware would delete some of your files and convert folders into executable files. Granted, the likelihood of a random folder miraculously transforming into a single executable file was kinda "out there" but I figured I'd check it out and use that as a teaching moment for those interested in venturing into malware analysis. So I tasked them to bring me a sample of the malware so I could take a look at it and maybe figure it out. I advised one of them to download DumpIt  and then extract the memory dump from an infected computer using a clean flash disk and then bring it to me. How do you do this exactly? here's how: Download DumpIt . It's a portable
Post a Comment
Read more

How I Recovered my Corrupted 2TB Hard Drive without having to copy everything to another Drive

So, a little back story. I have a 2 Terabyte external hard drive that's split into 3 partitions for backup; one for entertainment, one for work and one for personal projects. A friend of mine had a Lenovo laptop that was having challenges with installing WLAN drivers (you'd install the drivers and they'd keep giving an error that drivers aren't working. If you tried to uninstall them, they'd just reappear...but that's a whole different story). Anyway, my friend decided to roll-back from Windows 10 to Windows 8 and wanted to copy one of the test builds from my 2TB HDD so I lent it to him. Little did I know that that Lenovo laptop had other plans for me. Upon connecting the external hard drive to the Lenovo laptop, it immediately read it as a FAT32 formatted drive (it was actually NTFS formatted) and had 1.82 TB free space of the "actual" size 1.82 TB. Where panic would have ensued for many, I managed to keep in the growing irritation at such a thing
1 comment
Read more