As an intelligence agency, DIA's activities were classified. More than that, many DIA facilities were black sites, never officially existing, with numerous field caches hidden across the continental United States to aid field operatives. The secrecy allowed the Agency to maintain an extensive intelligence network abroad and on the domestic front, comprising human intelligence, signals intelligence, data processing, and more. To maintain secrecy the DIA had to go to great lengths at times, such as when Slocum's Joe #38, the cover operation for The Switchboard, had to deter Lexington customers. Ever increasing customer traffic buying overpriced coffee and donuts warranted increasingly drastic measures, such as halving cleaning, deliberately misleading customers, and even deploying hydrogen sulfide. The DIA also participated in the apprehension of Wan Yang, a Chinese field agent, in Maryland.
The DIA's technological capabilities were more advanced than many branches of the government. The P.A.M. Initiative was one of the most ambitious, daring, and most importantly, successful projects, resulting in the creation of a data processing system that allowed the Agency to predict the actions of foreign entities. By crunching the vast amounts of data provided, PAM could provide analyses or suggest corrective measures to achieve specific goals. Its first major success was stabilizing the situation in the Taiwan Strait, following the Pascale Incident.
After tapping it into all the military and civilian agency intelligence databanks, combined with greatly increased funding, the PAM project carried out at The Switchboard black site, PAM provided a decided edge against China in terms of intelligence. As it developed, PAM was used not just to process data, but to determine the likelihood of various military scenarios playing out, such as determining the likelihood of a coordinated nuclear strike by China and the USSR six months into the Chinese invasion of Alaska (June 2067).
While being one of the more technologically advanced government branches, the DIA still commissioned work to outside corporations, such as for the creation of the custom, multi-million dollar mainframe CRYPTOS created by RobCo. CRYPTOS was intended for use in "a top secret government project," but the DIA pulled the contract just as work was completed on the mainframe. Zack Hayes, a RobCo employee, was able to sell CRYPTOS to Frederick Rivers before the Great War to recover some of the money used to make it.
The DIA would also contract the Vault-Tec Corporation for the development of Project SERAPH. Seraph would have been an experimental Class-IV hypergenetic virus intended to penetrate high-security defense and intelligence mainframes. The Great War occurred before the project progressed past the prototype stage, but the overseer of Vault 96, Erik DeMarcos held onto the holotape with work on the virus. He hoped to use it to disable the vault's mainframe and let everyone escape the vault. Erik worked on the virus for almost three years, and after its completion the group attempted to leave the vault. A superseding protocol not on the vault mainframe activated just when they thought they would actually make it out, and remaining members of Vault 96 were killed by the vault's automated security.
- Naval recruiting center, Maryland: Field office established to apprehend Wan Yang.
- The Switchboard, Massachusetts: A black site below the Lexington Slocum's Joe shop in New England, used to create the Predictive Analytic Machine. The facility was repurposed into the headquarters of the Railroad until the Institute attacked and put the facility out of action. Further Railroad missions have the Sole Survivor seek caches left around the Commonwealth by the DIA.
- Monitoring stations A-31 and B-19: In November 2075, agents here spotted unidentified submarines. These contacts were rumored to be stealth subs of the Chinese.
- Deacon: " "
- Jackpot (quest)
- The Switchboard terminal entries; terminal, Hindu Kush Report
- The Switchboard terminal entries; terminal, Slocum's Joe Weekly Update
- Turtledove Detention Camp terminal entries; terminal, Public Release: Person Of Interest
- Turtledove Detention Camp terminal entries; Terminal, Bulletin: Yang Capture/Transfer
- Naval recruiting center terminal entries; DIA Officer's terminal
- The Sole Survivor: "Nice. That sounds pretty high tech."
P.A.M.: "Correct. The cache belonged to the Defense Intelligence Agency. The DIA's technological capabilities were more advanced than many branches of the government. You only have to secure the cache. Runners will transport contents on a separate timetable. Terminating human/machine interface."
- The Switchboard terminal entries; research terminal, > Section 1091/1092 Report
- The Switchboard terminal entries; research terminal, > 2067 Jun 19
- Riverside Manor terminal entries; Cryptos terminal, About CRYPTOS
- Riverside Manor terminal entries; Frederick's Terminal, Zack Hayes, 6/15/77
- Vault 96 terminal entries; Overseer's terminal, Project SERAPH, Executive Summary
- Vault 96 terminal entries; Overseer's terminal, Encrypted Logs, Personal Log - 11/10/77
- Vault 96 terminal entries; Overseer's terminal, Encrypted Logs, Personal Log - 8/31/80
- Vault 96 mainframe lab recording
- The Switchboard terminal entries; research terminal, 2075 Dec 17