Some web applications send unnecessary information to attackers
Surfing the Side
Sometimes error messages or log entries are too verbose for their own good, disclosing valuable information to attackers.
If you believe the movies, expert hackers only need to type a few cryptic characters at the command line to gain full access to the target within seconds. In reality, however, attacks on IT systems are usually not so easy to accomplish. Instead, the attacker sometimes needs days or weeks to succeed. During this time, the intruder explores the system to find a way around defensive measures, determines the best strategy for the attack, and avoids telltale log entries. Such attacks often occur in several successive steps and are called side channel attacks if they exploit hidden information just from observing the target system.
If this scrutiny relates to the hardware, it can include runtimes, processor power consumption, or electromagnetic radiation; if the intruder is focused on software resources, the attack might center on error messages or log entries. An intruder who is looking for information on the software might try to find out the version and patch level of the operating system, the database, the network components, or any active applications. The study might also include file paths to confidential data or configuration files.