uses character replacement  environment variables and XOR encoding to obfuscate code. 's backdoor code is a multi-layer obfuscated encoded and compressed blob. (Citation: FireEye MuddyWater Mar 2018)(Citation: ClearSky MuddyWater Nov 2018)  has used PowerShell code with custom string obfuscation 
Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request. ### Instruction: List the MITRE techniques contained in the text. ### Input: uses character replacement  environment variables and XOR encoding to obfuscate code. 's backdoor code is a multi-layer obfuscated encoded and compressed blob. (Citation: FireEye MuddyWater Mar 2018)(Citation: ClearSky MuddyWater Nov 2018)  has used PowerShell code with custom string obfuscation  ### Response: T1027.