For home use, what is the best way to deal with viruses that could be on external storage, which seems like a great way for hackers to persist on your system even after a reformat. Maybe the best practice is to just not store file types that are often hacked like PDF, flash, etc? Or is Dropbox and Google Drive good enough at detecting malicious files?

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    Force your ISP to use a CASB (Cloud Access Security Broker) – sandyp Jul 16 '16 at 23:10
  • If you're worried about unauthorised modification, hash your files and store the hash in a different place you trust (if it's just one file you are concerned about you could even just print the hash out and stick it next to your desk). Then before you open you can validate the hash... it will change on modification of course so not great if you need to modify a lot. – Matthew1471 Jul 16 '16 at 23:17
  • @Matthew1471 Which tools/languages would you use to automate that for thousands of files worth many gigabytes? – CarlGammaSagan Jul 17 '16 at 0:05
  • @Sandeep Could we really force residential Comcast to use a CASB? – CarlGammaSagan Jul 17 '16 at 0:06
  • Look up the md5sum or sha1 sum Linux command line. It can get the hash values of loads of files recursively and output them to a text file. You could then use grep to find the hash value of the filename in the text file and update it everytime you make a change. Or perhaps write a small bash shell script to get the hash values then compare them automatically every x day or something. But it might take a while to do that every day or slow your machine down. It's been a while since I did that so can't remember the exact commands but it's simple enough if I remember correctly – Lmnoppy Jul 17 '16 at 0:22
up vote 0 down vote accepted

Is this your own home machine? If it's a work network I would just block Google drive, Dropbox etc. People tend to take things home and work on them but means you have no control over the company data.

With that said I looked around a bit and it really depends on the provider some scan some don't and leave it to you to have a scanner installed. So I would just do some research on a provider before you use their services, at least that way you'll know where you stand.

I found the following in the security section about Google Drive.

Virus scanning: Google Drive scans a file for viruses before the file is downloaded or shared. If a virus is detected, users can't share the file with others, send the infected file via email, or convert it to a Google Doc, Sheet, or Slide, and they'll receive a warning if they attempt these operations. The owner can download the virus-infected file, but only after acknowledging the risk of doing so.

Only files smaller than 25 MB can be scanned for viruses. For larger files, a warning is displayed saying that the file can't be scanned.

I didn't find much on Dropbox except the Dropbox help page.

Dropbox will sync any files added to it, so if someone syncs a virus or malware file, it will be synced to any computers linked to the account. Other users' accounts and computers may also be affected if the virus or malware is in a shared folder. Malware files are generally not activated unless you click on them to open them. For this reason, just as with files from any other source, we recommend that you follow good security practices, such as running anti-virus software and exercising due caution when running unknown files from other computers.

I also found another question related to this Does Dropbox offer any protection against infected files?

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    Yes, it is home use. It seems like such a big hassle to deal with potential viruses that could be lurking in Dropbox, Google Drive, and external hard drives. Targeted attacks could easily bypass AV blacklisting. Even widespread viruses could easily persist on our systems because Dropbox and external hard drives have no AV. – CarlGammaSagan Jul 16 '16 at 22:04
  • You can tell your AV to scan external drives and your dropbox folder. Its the nature of AV they detect known viruses, trojans and other malware (signiture based). they cant detect unkwown, there's a alot of research going into anomaly based detection but not sure if it would come to home users yet. What av do you use? – Lmnoppy Jul 16 '16 at 22:48
  • Yea, that's true. But many previous news stories about many AV companies and Google's Project Zero do not inspire a lot of confidence in AV companies in general. I'm using Avast for Windows and not using AV on my Mac or Linux/Unix now but maybe I should start? Have any recommendations? – CarlGammaSagan Jul 16 '16 at 22:56
  • Yeah you should have AV on all your machines, i never understand why people say you don't. for Linux ClamAV Antivirus is the most used i think. For Mac i cant say, i don't really use Macs that much. It does suck and they do get a lot of flack for being slow but there isn't much they can do other than research or just politely ask hackers what malware they have made recently. And yeah you can just tell Avast to scan and watch your external hard drive. – Lmnoppy Jul 16 '16 at 23:10
  • The AV companies do have a pretty hard job relying primarily on blacklisting . I've heard that whitelisting like in the mobile app stores is a much better model, already adopted in Mac OS (though the user can override it, just like Android sideloading). Perhaps whitelisting will be the trend in the future if consumers really push for it. Especially against targeted attacks (which can likely happen to the personal electronics of engineers at big companies), whitelisting seems so much better. – CarlGammaSagan Jul 16 '16 at 23:54

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