Enter the below codes as the password to activate the desired cheat mode.

WOOWOO - Sirens
SUPACAM - Enemy fall cam
BENIHILL - Gav's mad cars
ALSECRET - All secrets

For infinite shields press Left + L1 + R2 + Square during the briefing
For infinite weapons press Left + L2 + R1 + O during the weapon review.

Here are the passwords for each level

Level 2 - KJOXAAAA
Level 3 - UIXZAAAA
Level 4 - MKFHRFAA
Level 5 - WHLTMIAA
Level 6 - YITSRFAA
Level 7 - UWCQAAAA
Level 8 - MYKXQFAA
Level 9 - YIOQMIAA
Level 10 - CJWGRFAA
Level 11 - IKFNIVDA
Level 12 - GVFSAAAA
Level 13 - MGIZAAAA
Level 14 - EIQGRFAA
Level 15 - QSTZMIAA
Level 16 - EEIQRFAA
Level 17 - CHYRAAAA
Level 18 - UGZKAAAA

Level 19 - KFPGRFAA
Level 20 - YCQGNIAA
Level 21 - ICZINIAA
Level 22 - WHCIAAAA
Level 23 - KTUWQFAA
Level 24 - YQVWMIAA
Level 25 - IQEZMIAA
Level 26 - EGXTVCAA
Level 27 - SRPIMIAA
Level 28 - CRAUVCAA
Level 29 - ODHDWCAA
Level 30 - CPZRMIAA
Level 31 - YOVYMIAA
Level 32 - YAXTRFAA
Level 33 - CRZOVCAA
Level 34 - QOAPRFAA
Level 35 - OPLRMIAA