ROL

Created the Monday 18 March 2019. Updated 6 months, 2 weeks ago.

ROL, or Rotate Left, is a simple encoding algorithm similar to the Caesar Cipher. In the ROL algorithm, each letter of the plaintext is replaced with a letter that is a fixed number of positions down the alphabet. For example, if the rotation value is 3, then the letter "A" would be replaced with "D", "B" would be replaced with "E", and so on.

ROL is a monoalphabetic substitution cipher, meaning that each letter of the plaintext is replaced with the same letter of the ciphertext every time it appears. This makes ROL relatively easy to break, as frequency analysis can be used to determine the rotation value and decrypt the ciphertext.

Despite its weaknesses, ROL is still a popular algorithm for teaching the basics of cryptography. In the context of malware, ROL can be used to encode the payload or communication channels in order to avoid detection and analysis.

Technique Identifier

U0704

Technique Tags

ROL Caesar Cipher Encoding algorithm Plaintext Ciphertext Rotation value Monoalphabetic substitution cipher Frequency analysis

Featured Windows API's

Below, you will find a list of the most commonly used Windows API's that are currently utilized by malware authors for current evasion technique. This list is meant to provide an overview of the API's that are commonly used for this purpose. If there are any API's that you feel should be included on this list, please do not hesitate to contact us. We will be happy to update the list and provide any additional information or documentation that may be helpful.

isalpha

Code Snippets

Description

The original message is first encoded using the ROL algorithm and the defined rotation value. The encoded message is then printed to the screen. The same rotation value is then used to decode the encoded message, resulting in the original message. This example demonstrates how the ROL algorithm can be used to encode and decode messages in a simple and easily reversible way.

# Define the original message to be encoded
message = "Hello, world!"

# Define the rotation value
rotation_value = 3

# Encode the message using the ROL algorithm and the defined rotation value
encoded_message = ""
for char in message:
  if char.isalpha():
    encoded_message += chr((ord(char) - ord("A") + rotation_value) % 26 + ord("A"))
  else:
    encoded_message += char

# Print the resulting encoded message
print(encoded_message)

# Decode the encoded message using the ROL algorithm and the same rotation value
decoded_message = ""
for char in encoded_message:
  if char.isalpha():
    decoded_message += chr((ord(char) - ord("A") - rotation_value) % 26 + ord("A"))
  else:
    decoded_message += char

# Print the resulting decoded message
print(decoded_message)

Additional Resources

External Links

The resources provided below are associated links that will give you even more detailed information and research on current evasion technique. It is important to note that, while these resources may be helpful, it is important to exercise caution when following external links. As always, be careful when clicking on links from unknown sources, as they may lead to malicious content.

https://blog.malwarebytes.com/threat-analysis/2013/03/obfuscation-malwares-best-friend/

ROL