The message, which went out to users of Symantec's DeepSight advanced alert system around 8:40 p.m. Eastern time, had a subject head that simply read: "DeepSight Increased ThreatCon from 1 to 4 Alert."
ThreatCon uses a 1-4 scoring system, with 1 being the least alarming threat level and 4 the most dire, to indicate Symantec's take on the current state of Internet security. According to the company's own definition, Level 4 is regarded as a "Full alert" and is reserved for those times when "extreme global network incident activity is in progress." The definition goes on to say that "implementation of measures in this Threat Condition for more than a short period probably will create hardship and affect the normal operations of network infrastructure."
Symantec has never set ThreatCon to Level 4. In fact, even a Level 3 is rare. One of the last times the Cupertino, Calif.-based security company issued a Level 3 alert was in May 2004, when the Sasser worm was on the rampage.
In the body of the e-mailed alert, however, careful readers found the words "Summary: threatcon test threatkhanh otrs" buried among several links.
The alert was a false alarm, Symantec said just over an hour later in a follow-up message at 9:45 p.m. Eastern time. "The DeepSight Threat Management System is NOT at ThreatCon 4. At 18:40 MST on September 21, 2007 an erroneous ThreatCon 4 update was issued through DeepSight TMS due to product testing. This ThreatCon 4 update should be disregarded."
A similar message posted on the DeepSight Threat Management System Web-based console ended with: "The ThreatCon has been returned to the correct level, ThreatCon 1."