Enter the following password, even though it will say bad password, it'll still work:

TTOPFSECRETT

At the password screen enter the following code:

AFQMOJGPVTPG

You will now be able to get to the last misssion.

LEVEL 2,Subpen area:ABEMJQLNVTPG
LEVEL 3,Russian EmbassyGLIESHVIRLL
LEVEL 4,KGB WarehouseQRFFSITJMNI
LEVEL 5,KGB HQ:EHNJHSURWJMP
LEVEL 6,Security Hallway:GDPSISJOWUAN
LEVEL 7,Underground Sewage Plant:GGHIHSJVWRML
LEVEL 8,Security Hallway:GQOFISKTLMAI
LEVEL 9,KGB HQ:IGCJMJMVMRBL
LEVEL 10,Russian Embassy:IQDSNJNTOMCI
LEVEL 11,IMF HQ:IJENMUNHONCJ
LEVEL 12,IMF HQ:IMQPNHNKOSCM
LEVEL 13,ImfirmaryBFROUOPPWDB
LEVEL 14,CIA RooftopMGKPUPKQSDM
LEVEL 15,CIA Mainframe ComputerJGNOUPHQNDJ
LEVEL 16,CIA Rooftop:KEJPPUPSAKEE
LEVEL 17,Waterloo:HDGGFPKQMOBC
LEVEL 18,Train:IGILGPMLMYBO
LEVEL 19,Train:HDGOFTKQMOBC
LEVEL 20,Train Roof:IGJDGTMLMYBO
LEVEL 21,Lundkvist Base:NGHSMGQTXMGI
LEVEL 22,Tunnel:MOEEOJGHVXJH
LEVEL 23,Mainland:MKEHTJSSWJD

Enter the following password, even though it will say bad password, it'll still work:

BIONICJUMPER

Enter the following password, even though it will say bad password, it'll still work:

IMTIREDTODAY

Enter the following password, even though it will say bad password, it'll still work:

SCAREDSTIFF

Enter the following password, even though it will say bad password, it'll still work:

GOOUTTAMYWAY

Enter the following password, even though it will say bad password, it'll still work:

SEECOOLMOVIE