March 15, Softpedia – (International)
A report by Mandiant focusing on advanced persistent threats (APTs) outlined several findings, including that there are on average 243 days between an attacker gaining access and when the attack is uncovered.
Source:
http://news.softpedia.com/news/It-Takes-a-Company-243-Days-to-Discover-a-Sophisticated-Attack-Study-Shows-337342.shtml