The only way the PS4 can get a virus is if someone bypass all 50+ layers of Sony's security and then on top of that write a virus program for the PS4 software using the root key, then hacking all 50plus layers to the PSN itself to write a PS4 update that has the virus embedded and then push that update to the PSN services layer that has to be approved from Yoshida-san himself before going on the production floor. So the hacker will have to hack Yoshida-san and all 50+ of his security layers to then give the update the go ahead for production. So in short... no the PS4 cannot get a virus. This is why they patched Linux in the PS3 because Linux wasn't secure and left the PS3 open to viral attacks.

Dude every program is sandboxed, even the webkit have its own sandbox.

@C-H-E-F:

None of that is necessary. A simple browser scripting attack could load a virus into the system. It just needs to be digitally signed so that the system recognizes it as official software. Hackers have spoofed the sigs before on both the PS3 and PSP. Not sure if they have access to them yet on the PS4, but it is technically possible.