Page 37 - CISSO_Prep_ Guide

percentage of data contamination comes from invalid input, the
first step to protecting the integrity of the data in our systems
and the integrity of the processes that manage the data is to
enforce checks and validation of data being input to the system.
Input data may originate from users, customers, or other
processes. The general rule is to trust nothing! Validate all input
data to ensure it is consistent with the rules - within acceptable
limits, values (alphabetic or numeric, special characters, or
symbols). This will be the first line of defense against integrity
problems.

The next step is to ensure that the processing of the data is
correct - the right account is updated with the right amount!
Arithmetic operations and calculations have to be checked to
ensure completeness (no transactions were missed), correct
addition, rounding, and storage.

Log the transaction in case a follow-up is needed - who made
the change, what change was made, and when the change was
made, sometimes even where the change was made from. The
logs should also be protected so that a user is not able to hide or
delete their activity. While processing data, the memory areas
allocated to the process need to be re-initialized before re-use to
prevent data contamination or disclosure.

The integrity of data may also be compromised during the
output process if the data is not displayed correctly - the output
field is too small, or the last transaction is not written to a file or
report.

Several sources also advocate the inclusion of another part to the
information security triad - the aspect of non-repudiation. To