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Can I attack a PC via the VGA port? Is VGA one way or does it accept data from the other side?

How about HDMI or DVI?

And if so, are there known malware or PoCs to do that? or is it theoretically fantasy?

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Same question on superuser.com/questions/79768/… –  Peanut Aug 21 '12 at 17:02
    
its not quite the same. I am not asking about malware, I am asking about purposely using the VGA or HDMI to attack the computer –  Nick Ginanto Aug 21 '12 at 17:12
    
I don't understand what distinction you are drawing between "malware" vs "attack". It looks like the same question to me, as far as VGA goes, and all of the answers there apply to your question as well. The main difference here is that you have also asked about HDMI or DVI. –  D.W. Aug 21 '12 at 19:27
    
By malware I mean any software that was made intentionally on harming the target by premade technique. By attack I mean that a human is on the other side of the cable trying everything from code injection to denial of service to even just be able to affect in some minute way on that computer in any way. Also it can be a PoC that haven't been weaponized yet. –  Nick Ginanto Aug 22 '12 at 3:18
    
Well, you can deny them the service of video output, that's for sure. –  David Houde Sep 14 '13 at 8:55
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4 Answers

VGA and HDMI are not one-way; besides the main send-pictures functionality, there is some low-bandwidth bidirectional communication. This is how a computer can "know" that a new display was connected, and what resolution to use on that display. In the case of VGA, this was a backported feature (VGA displays from the early 1990s could not do that).

Theoretically, this could be exploited, if (and only if) there is some weakness in the receiving part (the display card and its driver). The protocol is not complex (no TCP/IP stack involved) so exploitable security holes should be rare.

Usually, a malicious display can do much more evil by simply logging a copy of everything that is displayed. For instance, I have an account in a bank, such that for online banking I "type" a password by clicking on semi-randomly located buttons. A screen logger grabs the password easily in such conditions (ironically, that system was meant to thwart keyloggers). Therefore, the usual wisdom is that if your display is malicious, then you already have bigger problems.

Note: some displays also double as a USB hub -- and weaknesses in USB protocols have been exploited (e.g. the "PS3 Jailbreak" from 2010). For common PC, the USB link is an extra plug, but these things may change. For instance, Apple computers now use the Thunderbolt interface which is fully bidirectional and uses a rather complex protocol, where security holes are quite plausible.

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There's a DoS condition in some earlier drivers for DVI-D graphics cards, on single core machines, where the display device can repeatedly poll the machine for supported HDCP modes and lock the driver at 99% CPU usage. It's relatively easy to demonstrate using a microcontroller (e.g. Arduino) and a computer. It may still be possible, and I wouldn't be surprised if certain VGA cards / drivers would fall for the same issue with polling for resolution capabilities. –  Polynomial Aug 21 '12 at 17:43
    
Sadly, I can't find the page where I saw that demo. I might dig out the HDCP specs and DVI-D datasheets later and see if I can reproduce it. –  Polynomial Aug 21 '12 at 18:05
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An alternative to infecting the computer might be to make a device that sits in the middle (between the computer and monitor) and which saves screenshots on a set interval.

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Not really relevant to the question, he's asking how to attack/infect via the ports in question, not for general advice. I would down vote but 256 rep is too nice a number to have... –  Peanut Aug 21 '12 at 21:40
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@peanut hmm true.. Was already doubting to post this as comment. I will next time –  Luc Aug 21 '12 at 21:55
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VGA and DVI? I dont think so. For HDMI, there was no PoC yet, but as it can carry the Ethernet, break-in over HDMI is absolute possibility.

With new TV sets there is a new range of attacks:

  • DVB-T code injection on Smart TV - user browses the channel, and runs malware on his tv
  • Smart TV WebKit / Android - HTML-5 engine is using internet connection hence it's hackable as any other Android device with browser.
  • HDMI supports ethernet, so if you hack into Smart TV, you can gain control of other devices via network interface it supports, like UPnP is known to be usually vulnerable to attacks:

http://www.hdmi.org/manufacturer/hdmi_1_4/hec.aspx

This is next-generation of hacking and a new class of home and business intrusion. The next thing is to open a fridge and find a software virus in it.

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Can you please elaborate on the circumstances that make this possible? –  Nick Ginanto Aug 22 '12 at 3:19
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The plug-and-play feature of a DVI port utilize the I2C (i-squared-C) bus, a low speed serial bus that internonnect the two endpoints and allow negitiation of plug and play features. Potential for abuse, but I don't know of any POC code.

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