For each sample, we are going to use the older version of 7zip (15.05) since newer versions do not support the unpacking of “.nsi” script used to control the installation tasks.
CRYPTER MEANING ARCHIVE
Note: A NSIS-based installer package is an archive that can be unpacked using 7zip. Let us take a quick look at the overview of some variants we’ve seen. Crypter Evolutionĭuring our continuous monitoring of this crypter, we observed 3 different variants in the past year. Unknowing users open the program, which will force the crypter to decrypt itself and then release the malicious code. They then send these programs as part of an attachment within phishing emails and spammed messages. For this reason, one input source file will never produce an output file that is identical to the output of another source file.Ĭybercriminals build or buy crypters on the underground market in order to encrypt malicious programs then reassemble code into an actual working program. They use algorithms with random variables, data, keys, decoders, and more.
Polymorphic crypters are more advanced than static crypters.Having separate stubs for each of these clients makes it easy for malicious actors to modify a stub once it is detected by a security software. Static/statistical crypters utilize stubs to make each encrypted file unique.Depending on the stub the crypter uses, they can be classified as static/statistical or polymorphic. Types of CryptersĪ crypter contains a specific crypter stub, which is the code used to encrypt and decrypt forms of malicious code. Crypters are used by cybercriminals in order to create malware that bypasses security programs by presenting itself as being a harmless program until it is installed. This makes it harder to detect by security programs.
CRYPTER MEANING SOFTWARE
What is Crypter Malware?Ī crypter is a specific type of software that has the ability to encrypt, obfuscate, and manipulate different kinds of malware.
We will also include an in-depth analysis of a recent NSIS-based crypter variant that we encountered. In this article, we will re-visit the NSIS-based crypter that we came across in the past couple of years. Although a lot of legitimate developers are using it, threat actors take advantage of using this to spread malware. This tool is flexible and can let you bundle several components such as executable files (EXE), DLL, configs, etc., together with a script that allows you to control the logic of its installation.
CRYPTER MEANING INSTALL
What is NSIS?Ī quick overview of NSIS (Nullsoft Scriptable Install System): it is an open-source script-driven tool that can be used to create Windows software installers. We have seen several ways of obfuscation implemented with the installer that decrypts and directly loads the malware into memory without dropping its file to the disk. Malware such as FormBook, AgentTesla, GULoader, just to name a few, have been using NSIS as their loader. We have been observing that malware is being distributed via NSIS-based crypter.
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