Simple Ciphers

Ciphers are often used in malware to obfuscate malicious code or encrypt data. This chapter focuses on understanding and implementing simple ciphers that are used in malware. In other words, this chapter takes a step back from the complexities of advanced cryptography and focuses on the foundations with simple ciphers. You will be given an overview of basic encryption methods such as Caesar Cipher, substitution cipher, and transposition cipher, which are commonly used for basic data obfuscation. We’ll dive into the mechanism of these ciphers, illustrating their strengths and weaknesses. This chapter also provides practical examples of how these ciphers have been used in real malware and explains why, despite their simplicity, they can still pose a challenge to malware analysts.

In this chapter, we’re going to cover the following main topics:

• Introduction to simple ciphers
• Decrypting malware – a practical implementation of simple ciphers...