Malware analysis: searching for dots
Reader Chris submitted a suspicious attachment. It is a 7-Zip file.
As you probably know, I like to do static analysis without extracting malware to disk, but by piping it into a chain of tools.
This can be done with 7-Zip too. Here is the content of the file:
It contains a single VBScript file: IMG_0107.vbs.
I can look at the script by extracting it (command e) and writing the output to stdout (option -so). This way, I can read the script without writing it to disk:
Take a look at the last line in the screenshot: it's a simple obfuscation of the string .responseBody. This is a strong indication that this VBS script is a downloader.
When analyzing obfuscated source code like VBA and VBS, I like to grep for lines with a dot character (.), as this gives an overview of method calls:
Not only does this output clearly shows that this is a downloader that will write to disk and execute the payload, it also reveals URLs, a User Agent String and keywords separated with the string "Swing".
Let's deobfuscate the URLs first:
With "re-search.py -n str" I extract the strings:
Then I remove the double qoutes with sed:
And finally, I split the string with sed by replacing ^ with newline:
Unfortunately, the URLs were dead when I did the analysis.
I can extract the "keywords" with the same method:
From this we can deduce that the downloaded file is written to a temporary folder in file UUmDBYNd.exe.
Another method I like for quick analysis of obfuscated source code, is just to extract strings with my re-search.py tool:
Didier Stevens
Microsoft MVP
blog.DidierStevens.com DidierStevensLabs.com
Comments
Anonymous
Dec 3rd 2022
9 months ago
Anonymous
Dec 3rd 2022
9 months ago
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<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
Anonymous
Dec 26th 2022
8 months ago
Anonymous
Dec 26th 2022
8 months ago
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<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> public bathroom near me</a>
Anonymous
Dec 26th 2022
8 months ago
<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>
Anonymous
Dec 26th 2022
8 months ago
Anonymous
Dec 26th 2022
8 months ago
https://defineprogramming.com/
Dec 26th 2022
8 months ago
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/
https://defineprogramming.com/
Dec 26th 2022
8 months ago
rthrth
Jan 2nd 2023
8 months ago