IT Forensics · Linux

Forensic analysis of Shell environment variables – assessing the configuration context of individual sessions

Environment variables influence the behaviour of shells and programmes, for example through path specifications, library settings or proxy configurations. They can be set at system-wide level, or on a user- or session-specific basis.

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Certain environment variables, such as those relating to library integration, are regularly and deliberately exploited to manipulate the behaviour of programmes or circumvent security mechanisms.

Why LanCologne?

Since its foundation, LanCologne has specialised in professional IT forensics. Our staff have decades of experience in the field of information technology and assist companies, solicitors, private individuals and, on a regular basis, the courts in the technical investigation of complex digital matters.

The examination is, as a matter of principle, carried out exclusively on a forensic copy, a forensic image or a data source captured in a technically equivalent manner that preserves the integrity of the evidence. The original evidence remains unchanged and is stored in a manner that preserves its integrity.

Our services

We analyse relevant environmental variables from existing configuration files and, where available, from process information relating to running systems, and check for signs of deliberate manipulation.

Typical areas of application

•Detection of tampered library or path settings
•Investigation of session-specific configuration changes
•Analysis of proxy and network configurations for individual sessions
•Supplementing process and persistence analyses
•Incident Response on Linux Systems
•Judicial and non-judicial expert reports

This is how environment variables are processed

After the backup, system-wide and user-specific configuration files are checked against defined environment variables. For running systems, session-specific environment variables for individual processes are also collected via /proc and examined for atypical or security-relevant settings.

Why is this classification relevant from a forensic perspective?

Certain environment variables can be specifically exploited to manipulate programmes or circumvent security mechanisms, which is why they are checked separately if there is reason to suspect such activity.

Even inconspicuous environmental variables, such as proxy settings, can provide valuable insights into the actual network communication taking place during a session and are therefore included in the overall assessment.

Frequently Asked Questions

Which environment variables are particularly relevant from a forensic perspective?+
These include, amongst other things, those relating to library integration, the search path for executable files, or network and proxy settings.
Are environment variables stored permanently?+
Only insofar as they are set in configuration files. Variables that are purely session-specific can only be evaluated via process memory on running systems.
Can environment variables bypass security mechanisms?+
Yes, certain variables can be specifically exploited, for example, to trick programmes into using tampered libraries.

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