I just got off the phone with an investment firm where I have an account. About a month ago, they blocked online access to my account due to "malware or a virus" found on my PC or device. Since we had been overseas for most of that month, and according to their logs the time when the "virus or malware" was discovered was roughly 1pm on March 29th (and we were already out of the country), that means that the number of devices we could have logged on with is reduced down to only 4 (two Android phones, an Android table, and an iPad). The time stamp would have been roughly 1am the following day in the country we were visiting, about 1-2 days after we arrived. After talking with the customer service manager for some length of time, there has been no activity in my account, other than payroll deposits as expected, so I don't think anything untoward has occurred.
They refused to grant me access to my account until I'd had my devices / PC "professionally cleaned". I have no idea how they'd be able to know I'd done this, besides I'm a computer professional, and I'm reasonably certain none of my devices are infected with anything. Once I've done this, they will change passwords and usernames, etc. to allow me access to the account.
What I suspect actually happened was me trying unsuccessfully to log onto the account from my tablet (I vaguely remember something like this happening right after we got there, but didn't think much of it). I probably tried too many times and the account got blocked. Since I was trying from an out of the US IP address, this made it suspicious. That's my guess.
My actual question is, is it possible for a given website to be able to detect that the log on attempt is occurring from a device that has a virus or malware on it? I don't believe it's possible for them to sniff my devices, but I figured you guys would know better than me.