The purpose of a DHA is to find valid email addresses on a domain for future spam attacks. During a DHA attack, any addresses for which the recipient’s email server accepts email are considered valid and will be added to the spammer’s address database to include in future spam attacks.
For example:
Sample #1:
From: joannjasmin8xs@xxxxxx.com
Subject: land
Those journalists showed them a photograph.
Sample #2:
From: clariceboldin9cg@xxxxxx.com
Subject: okay then
They told her the shortest way.
DHA is more than just an annoyance for email recipients. Every successful DHA attack equals one or more email address being subjected to future spam/malware attacks. Furthermore, these attacks also generate a large volume of unnecessary workload and consume significant amounts of system resources on the recipient’s email server. Symantec is closely monitoring these attacks and will inform readers of any further developments.