Body message

The body message is a long-running key element of the INFRA ARG, the first ever element of it that was discovered.
It has strong ties to the Bunker computer code and Wasteland notes.

The body itself is likely Albert Hartman.

Finale has done a lot of work on cracking this part of the ARG, for further reference please see his Steam guide created for this.
It's located in reserve2 and is a code written on the sheet which covers a corpse in a side building.

Cracking the code

The code sequence for the body message is:

B1 C3 F1 B2 F2 C4 E4 G3 B2 G1 F4 B4 B2 G1 G2

Which translates to:

I will (F1(show?)) the truth (C4(code?)) to tell the right three words to the right person.

It is theorised that the right three words are "answer under ground".

The entire body message revolves around a series of letter-number references, which correspond to words that have been found in INFRA maps and textures. The following is a table containing all of the current keys and their corresponding words. Bold ones are in use by codes.

Key	Word	Source	Reliability
A
A1	What	See Steam Guide	Confirmed
A2	Happened	See Steam Guide	Confirmed
A3	To	See Steam Guide	Confirmed
A4	AH	See Steam Guide	Confirmed
B
B1	I	Central Note 1	Confirmed
B2	The	Central Note 1	Confirmed
B3	In	Central Note 1	Confirmed
B4	To	Central Note 1	Confirmed
C
C1	Is	See Steam Guide	Confirmed
C2
C3	Will	Central Note 1	Confirmed
C4	Code	S.N.W Reactor Infoboard	Likely (It fits)
D
D1	Other World	Bunker Drawing	Probable
D2
D3
D4
E
E1	IS	See Steam Guide	Confirmed
E2
E3
E4	To	Unconfirmed	Inferred from bunker computer code
F
F1	Show	Guess	Likely (It fits)
F2	Truth
F3
F4	3 Words	reserve2	Confirmed by Sewer monitor code
G
G1	Right	See Steam Guide	Confirmed
G2	Person	See Steam Guide	Confirmed
G3	Tell	See Steam Guide	Confirmed
G4
H
H1
H2
H3
H4	????E	Unconfirmed	Inferred from bunker computer code

Clues

The hint

The hint Zuntti gave us for this "code segment" is "BUN_BREAKER_CEN_CONTROL_VI_OFFICE_RE_SNW".
There are four clues here, each representing a location or map in INFRA.

"Bunker breaker, central control (room) (the control room in Central), Villa office, Reactor SNW (area)?"

Bunker breaker

This clue refers to the breakers outside the Bunker, in the Servicetunnel map. This has been confirmed by Zuntti's screenshot.
Possibilities here are the signs on the breakers themselves which have small text as follows:

(Breaker 1) Main text: TGD-SBC-4, small text: BR4 TGDNUM PO7 TGD1
(Breaker 2) Main text: HW-SBC-2, small text: BR4 HWNUM+1 O34 C87 EA2 N6

TGD could mean Two Gorges Dam, and HW is probably Hammer Valley Water Dam. Both breaker small texts have a "NUM" on them, prefixed by their name, with 1 being added to HWNUM.
Another possibility was the book with the bunker codes, however some codes are completely illegible and decoding with several bases does not result in anything of note.
Reading only the letters on breaker 2 reveals word "OCEAN". The breaker is assigned with number 2 so HWNUM+1 could be 3.

Comparing numbers to first letters of bunker computer yields: POR TGDU ODE COR EAU NG , which can be re-arranged into: ATOP UNDERGROU_D CORE

Central control

This clue refers to the control room in Central, where there are a few code possibilities.

Morse

The first one is the Central projector morse, which does not produce a code but a message/clue about "the right person".

Pegboard

The second one is the pegboard, which has two possibilities of its own: the pegs, the markers behind, and the unrelated notes stuck to the pegboard.
(Click this image for a HD, zoomable view.)

Pegs

These are the pegboard pegs, transcribed.
E means empty, P means peg and M means peg with marker.

MPMEEMPMPMEEEMPMPMPEEEMP
PMPMPPEPEEEEEEEEMPMPMPMP
(empty for 2 lines)
(break)
(empty for 4 lines)
(break)
MPMPMPEEEEMPMPEEEEMPMPMP
PMPMPMPMEEEMEMPEPMPMPMPM
(empty for 2 lines)
(break)
MPMPMPMPEEEEEEEEEEEEEEEE
PMPMPMEEEEEEEEEEEEEEEEEE
(empty for 2 lines)
(end)

Notes

Note 1

RT 34968 BG 125675567
HK 675756 B1 = I KK 32
32123 B2 = the 1231324
123 B3 = in 364363463
B4 = TO 423424234 423
54353 C3 = 1(KKKKKKKK)
= WRONG 234 OIYUIO
W1I1L1L1 = RIGHT tr45
YTIT NOT B5675675567
Maybe YTWE 91267867

Removing the clutter, we can solve B1, B2, B3, B4, and C3:

B1 = I
B2 = the
B3 = in
B4 = TO
C3 = WILL

Note 2

CODE: 13523523578
YOU HAVE TO REMEMBER
THAT OR YOU WILL GET
SOME RANDOM STUFF
I have no idea what is
the stuff you know (unreadable)
(unreadable)

Note 3

Villa office

See Villa woodboxes.

Reactor SNW

This clue refers to the secret SNW area of the Reactor map. The Reactor lights code is present here but does not seem to be connected to the body message, so it should be ignored.