Can the iPhone transfer PC viuses and keyloggers?

The answer to all of your questions is no, as long as your phone is not "hacked".

There are no known viruses for an iphone that has not been hacked & Apple does a very good job of insuring that all known security holes a plugged. If you don't hack your phone, you have nothing to worry about.

The iPhone does not support disk mode - to be used as an external drive. Although it is possible to transfer photos from the iPhone's Camera Roll, it is not possible to transfer photos from your computer to your iPhone's Camera Roll except for being transferred to your iPhone via the iTunes sync/transfer process, which is selected under the Photos tab for your iPhone sync preferences with iTunes.

Nothing can be installed on an iPhone from a received email or from a website except for a photo or a PDF file. A photo saved from a received email or from a website is stored in the iPhone's Camera Roll and a PDF can be saved from a received email to the iBooks application.

A JPEG, as a file, can have a virus placed within the file. However, in order to activate the virus, the file must be run. As the JPEG file is an image file, it will not be executed as long as the image is not processed by any other type of program. Again, you have nothing to worry about as long as your phone is not hacked.

I haven't read many reports about a JPEG file including a Windows virus, which must include an installer in order to install the virus when opening the JPEG or photo file.

A Windows virus cannot affect or infect OS X, and the iPhone runs an optimized version of OS X.

Photos transferred from your computer to your iPhone is a one way transfer process only - from your computer to your iPhone. Connect your iPhone to iTunes on another computer and photos transferred from another computer cannot be transferred in the opposite direction.

Email a JPEG or photo file that includes a Windows virus from your iPhone that was transferred from your PC to your iPhone to another poor Windows user and if the Windows recipient does not use antivirus software or does not keep their virus definitions up to date and the photo is opened on their PC, then they will get infected with the Windows virus. Your Windows PC - the PC any photos are transferred from should be running antivirus software as well along with anti-adware, anti-spyware, and any other anti-whatever that is required with that swiss cheese for security operating system.

If a photo file that includes a Windows virus is transferred to your iPhone, it cannot affect or infect the iPhone. The photo can be emailed to someone else as with any other photo.

The transfer of photos from your computer to your iPhone via the iTunes sync/transfer process is a one way transfer process only - from your computer to your iPhone. Apple does not support transferring these photos in the opposite direction. There is no option to do this with iTunes and there is no option to import these photos by your computer as it is possible to import photos from the iPhone's Camera Roll.

If you have an infected PC and transfer a JPEG file that is infected with a Windows virus to your iPhone and you send the photo that includes a Windows virus to a Windows user with an email, if the recipient does not run any antivirus software and opens the JPEG on their PC, their PC will become infected.

Transferring a file alone cannot infect a Windows PC. An infected file must be opened on the PC for the virus to be installed.

Since you are a Windows user, you've got much more to be so concerned about than the iPhone transferring a Windows virus from one PC to another. That is the least of your concerns as a Windows user.

What about programs like Phonedisk?
http://www.macroplant.com/phonedisk/

I got this and can store any files on my (non-jailbroken) iphone4.
Sure you couldn't have a self spawning virus that travels off your phone to infect a computer.

As with the virus-in-a-jpeg there is no way an iphone can "help" spread a virus.

Only YOU can move an infected file to the iphone (which cannot infect the iphone as such), and YOU then copy it to a new computer... then YOU have to execute it.
That's YOU being reckless.
Like if YOU drive with out a seat belt, or YOU drink and drive... there is no way Apple can save YOU from yourself.

But I believe your email account or web browser is more capable of spreading a virus then a non-jailbroken iphone.

That is for now... Apple might miss a line of code some day.
But then again, you'd still be more likely to get a virus from somewhere else.
So keep a good virus checker in place in any case.

Wjosten, what do you mean "As the JPEG file is an image file, it will not be executed as long as the image is not processed by any other type of program."? What kind of file would have to process it to activate a virus?

Years ago, researchers were interested in whether a virus could in fact be placed in an image file, like a JPEG file, and spread using the image file. While they succeeded in placing the virus in a JPEG file, they realized the virus would not execute or spread without another separate executable designed to extract the virus from the JPEG file. If you stop & think about this for a moment you'll realize how ineffective this is. In essence its not a serious threat at all.

While they succeeded in placing the virus in a JPEG file, they realized the virus would not execute or spread without another separate executable designed to extract the virus from the JPEG file.

There were some tests made where a file containing both a virus and image would be named: FileName.jpg.app (FileName.jpg.exe for Windows). On systems that are set to not show filename extensions (not a good idea, but often the default), the file appears as: FileName,jpg

If the file is opened by a picture display application, such as Preview, or is dragged onto the application's icon, it will act as a .jpg file and display the picture that is included in the file. If, however, the file is double-clicked, it will run the code included in the file, which can do anything allowed by the user's account (which might include installing a virus). It could also display the picture so as not to arouse suspicion.

To protect against this sort of attack, OSX added a warning for any downloaded files that are applications.

That is not true there has been a Trojan virus threat on the iPhone. And also hacking is not the term you should use for a phone that when do you hack it or you pay apple to hack it for you. It becomes twice the machine it was. Get a firewall i think norton's got them for sale!

That is not true there has been a Trojan virus threat on the iPhone.

The definition of a virus includes spreading from computer to computer or from device to device virally without the user's knowledge, so please name this Trojan virus threat for the iPhone and it can be acquired and installed how on the iPhone?