BASE85 Decoding With base64dump.py

Published: 2021-07-17
Last Updated: 2021-07-17 07:17:24 UTC
by Didier Stevens (Version: 1)
0 comment(s)

Xavier's diary entry "Multiple BaseXX Obfuscations" covers a malicious script that is encoded with different "base" encodings. Xavier starts with my tool base64dump.py, but he can not do the full decoding with base64dump, as it does not support BASE85.

I've now added support for BASE85: base64dump.py version 0.0.0.16.

(you can watch this video: "Adding BASE85 To basedump64.py", if you are interested to know what changes I made to my base64dump.py tool to support BASE85)

So, let's see how to use base64dump with Xavier's sample. As Xavier showed yesterday, this sample has the payload encoded as a list of hexadecimal string. So let's do hex decoding with base64dump: option -e hex. And option -n 10 for a minimum length of 10:

base64dump found 21 hexadecimal strings, with a minimal decoded length of 10.

These strings have to be concatenated together. We can achieve this with base64dump, by ignoring all whitespace (including newlines) and ignoring the string quotes (single quote '), like this:

Now we have extracted one single, long hexadecimal string. Let's selected and decode it:

This is again an hexadecimal string. Let's decode it with another instance of base64dump:

And this is the BASE85 encoded script. Let's decode that too:

And we end up with the same decoded script as Xavier found yesterday.

Didier Stevens
Senior handler
Microsoft MVP
blog.DidierStevens.com

Keywords: base85
0 comment(s)

Comments

What's this all about ..?
password reveal .
<a hreaf="https://technolytical.com/">the social network</a> is described as follows because they respect your privacy and keep your data secure:

<a hreaf="https://technolytical.com/">the social network</a> is described as follows because they respect your privacy and keep your data secure. The social networks are not interested in collecting data about you. They don't care about what you're doing, or what you like. They don't want to know who you talk to, or where you go.

<a hreaf="https://technolytical.com/">the social network</a> is not interested in collecting data about you. They don't care about what you're doing, or what you like. They don't want to know who you talk to, or where you go. The social networks only collect the minimum amount of information required for the service that they provide. Your personal information is kept private, and is never shared with other companies without your permission
https://thehomestore.com.pk/
<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> public bathroom near me</a>
<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> nearest public toilet to me</a>
<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> public bathroom near me</a>
<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> public bathroom near me</a>
<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> nearest public toilet to me</a>
<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> public bathroom near me</a>
https://defineprogramming.com/
https://defineprogramming.com/
Enter comment here... a fake TeamViewer page, and that page led to a different type of malware. This week's infection involved a downloaded JavaScript (.js) file that led to Microsoft Installer packages (.msi files) containing other script that used free or open source programs.
distribute malware. Even if the URL listed on the ad shows a legitimate website, subsequent ad traffic can easily lead to a fake page. Different types of malware are distributed in this manner. I've seen IcedID (Bokbot), Gozi/ISFB, and various information stealers distributed through fake software websites that were provided through Google ad traffic. I submitted malicious files from this example to VirusTotal and found a low rate of detection, with some files not showing as malware at all. Additionally, domains associated with this infection frequently change. That might make it hard to detect.
https://clickercounter.org/
Enter corthrthmment here...

Diary Archives