Data logs are computer generated data sets, collected through sensors. Data loggers are usually small, portable, battery powered devices, equipped with sensors, memory storage, and a microprocessor. They can be stand-alone devices, or can be used in conjunction with a computer. When used with a computer, the computer not only collects the data, but can also analyze it, and save the output.
Data loggers can be set to automatically gather data over a specified period—for instance, social media output around a particular incident.
Data logs have been used by human rights defenders to identify sources of hacking and internet surveillance. OONI, the Open Observatory of Network Interference, a smartphone application, uses network data to detect censorship, surveillance, and traffic manipulation on the internet.
Data logs can also be connected to environmental sensors to track air, water, or soil contamination over time.