NSA Exploit of the Day: DEITYBOUNCE

Today's item from the NSA's Tailored Access Operations (TAO) group implant catalog is DEITYBOUNCE:

DEITYBOUNCE (TS//SI//REL) DEITYBOUNCE provides software application persistence on Dell PowerEdge servers by exploiting the motherboard BIOS and utilizing System Management Mode (SMM) to gain periodic execution while the Operating System loads.
(TS//SI//REL) This technique supports multi-processor systems with RAID hardware and Microsoft Windows 2000, 2003, and XP. It currently targets Dell PowerEdge 1850/2850/1950/2950 RAID servers, using BIOS versions A02, A05, A06, 1.1.0, 1.2.0, or 1.3.7.
(TS//SI//REL) Through remote access or interdiction, ARKSTREAM is used to reflash the BIOS on a target machine to implant DEITYBOUNCE and its payload (the implant installer). Implantation via interdiction may be accomplished by nontechnical operator through use of a USB thumb drive. Once implanted, DEITYBOUNCE's frequency of execution (dropping the payload) is configurable and will occur when the target machine powers on.
Status: Released / Deployed. Ready for Immediate Delivery
Unit Cost: $0

Page, with graphics, is here. General information about TAO and the catalog is here.
In the comments, feel free to discuss how the exploit works, how we might detect it, how it has probably been improved since the catalog entry in 2008, and so on.
The plan is to post one of these a day for the next couple of months.