Revealing system data or debugging information helps an adversary learn about the system and form a plan of attack.
An information leak occurs when system data or debugging information leaves the program through an output stream or logging function.
Example: The following code prints the SAPFTP version information on the screen:
...
CALL FUNCTION 'FTP_VERSION'
...
IMPORTING
EXEPATH = p
VERSION = v
WORKING_DIR = dir
RFCPATH = rfcp
RFCVERSION = rfcv
TABLES
FTP_TRACE = FTP_TRACE.
WRITE: 'exepath: ', p, 'version: ', v, 'working_dir: ', dir, 'rfcpath: ', rfcp, 'rfcversion: ', rfcv.
...
[1] Standards Mapping - OWASP Top 10 2007 - (OWASP 2007) A6 Information Leakage and Improper Error Handling
[2] Standards Mapping - Security Technical Implementation Guide Version 3 - (STIG 3) APP3620 CAT II
[3] Standards Mapping - Common Weakness Enumeration - (CWE) CWE ID 497
[4] Standards Mapping - Web Application Security Consortium 24 + 2 - (WASC 24 + 2) Information Leakage
[5] Standards Mapping - Payment Card Industry Data Security Standard Version 2.0 - (PCI 2.0) Requirement 6.5.5
[6] Standards Mapping - Payment Card Industry Data Security Standard Version 1.2 - (PCI 1.2) Requirement 6.5.6