Safety of a PC when disconnected from the Internet

[feynman1]

Is a PC free from viruses when disconnected with internet?

 

[Filip Larsen]

Your question is a bit hazy, but no matter what situation you are thinking of the short answer is probably no.

Having a PC connected to the Internet is definitely the most significant general attack vector today (compared to, say, inserting an infected USB-drive or getting hit by a drive-by Bluetooth attack) but at the same time having the PC connected to allow its software to update security patches is also vital. Note that technically the weakness is not in the connection itself (1) but in the many software components or services that the operating system and applications are built from. Disconnecting at a particular time just means all those components for the time being is unable to communicate outside your PC, but they still contain all the data and state (including any virus) as before. If you take disconnect idea to the extreme and keep your PC off the Internet (and other connections, including unsanitised USB-drives) at all times then it is called air gapping.

Perhaps you can add a few more details about the situation you are thinking about to provide clues for a better answer?

Footnote (1): A bit of an analog to this could be to say "its not roads that gets you infected with human virus in your home, its friends and family traveling on them to visit you, or you to them, that makes virus spread". And just like if you don't meet anyone physically during a pandemic you greatly reduce risk of getting infected by human virus, the same goes for your PC. For instance, a significant malware vector is still PC users clicking on malicious links in emails or on webpages, corresponding, in the human virus analogy, to people themselves happily letting a person claiming their rich uncle sent him to give them one million dollar into their home so he can cough on them.

 

[MikeeMiracle]

Computer virus's were around a long time before 99% of the population knew what the internet was. It was transferred by floppy disks when people copied data between computers.

Most virus's (virii?) back then were destructive and made by people who thought anyone with less knowledge about computers than themselves didnt deserve to have a computer. These days it's more malware which aims to steal data from your.

The proper term for having a computer network disconnected from the public internet is "air-gapped" but even then, nation state actors have devised method of overcoming this. These methods include measuring magnetic fields from your CPU, power fluctuations in the supply, blinking an LED on your computer which is then picked up by a camera external to your PC like a security camera and even using the computer's speaker to emit sound inaudible to the human ear.

 

[Mark44]

Most virus's (virii?)

OT, but viruses will do just fine. Notwithstanding what you might see in a supermarket (e.g., banana's), noun plurals aren't formed by adding "'s".

 

[FactChecker]

Computer virus's were around a long time before 99% of the population knew what the internet was. It was transferred by floppy disks when people copied data between computers.

Most virus's (virii?) back then were destructive and made by people who thought anyone with less knowledge about computers than themselves didnt deserve to have a computer. These days it's more malware which aims to steal data from your.

The proper term for having a computer network disconnected from the public internet is "air-gapped" but even then, nation state actors have devised method of overcoming this. These methods include measuring magnetic fields from your CPU, power fluctuations in the supply, blinking an LED on your computer which is then picked up by a camera external to your PC like a security camera and even using the computer's speaker to emit sound inaudible to the human ear.

This is all true, but where you need to worry about things like this, there are almost certainly system administrators in a secure facility who are in charge of security. It's a very complicated thing. For home use, you probably can do ok with scanning any media, always updating good security software, and being careful on the internet. So we really need to know how the PC will be used (home private use, company use, classified use) before we can give a good answer.

 

[anorlunda]

I think the OP question is not well specified.

It is one thing for a consumer to protect themselves against the most common risks.

Even for consumers, I would define two tiers of risks. Those who visit risky sites (e.g. gaming, porn, hackers) and those who only visit less risky sites (e.g. PF).

If you are a person like Edward Snowden, the target of state-owned intelligence agencies, the precautions your security needs are sky high. You would probably need Snowden's expertise to have any chance of success. The most attacked users of course would be military computing in time of war.

The OP does not specify whether the PC is not connected to the Internet sometime, or forever. I had a Commodore Pet. It's software is all in ROM. There is no phone or net port, no USB, no disks, only a cassette tape. It would be very hard for a hacker to hack that machine, and there would be little reward for his efforts.

If you are asking about what's possible, versus what's practical, almost everything is possible. Even a distribution of your OS on DVD or online can not IMO be 100% sure that it is not compromised. Similarly, you can never be sure if your PC hardware has been compromised at the factory.

My guess that the OP question was about the most common risks, and risk management for an average consumer who connects to the Internet only sometimes. Yes, you can be slightly safer if you disconnect or shut down when you're not using the machine. If that's not the real question, then please elaborate.

 

[Dr Transport]

a computer can only be completely virus free if it has never been attached to the internet

 

[FactChecker]

a computer can only be completely virus free if it has never been attached to the internet

I think that is much too strong a statement. With reasonable care, I think one can be fairly safe. But it is good to be aware of the dangers.

 

[MikeeMiracle]

If your a home user and familiar with virtualisation then you can setup a "web facing" VM with a non-persistent disk. This disk does not save any changes to it so in effect you have a clean slate each time you turn it off and on again. That's probably about as safe as yor going to get as a home user, it does need some tech knowledge to setup though but not an insurmountable amount.

 

[russ_watters]

a computer can only be completely virus free if it has never been attached to the internet

And never receives information via other methods that can transfer executable code, such as disks (flash drives), a keyboard or a microphone. By nature, being infect-able is a consequence of the intrinsic purpose of most general purpose computers.

 

[FactChecker]

You can also get a virus on your PC if you use media like thumb drives, CDs, and DVDs. So you must be aware and careful with all your source material.

 

[MikeeMiracle]

To sum up, the stuff which does damage to your computer, i.e. Virus's you are still susceptible to which can be transferred by using other media. The stuff which steals your data, i.e. malware, you can protect from by having your computer disconnected from the internet. You could still get infected with malware via infected media, but without an internet connection there is no way for that information to leave your computer.