LSAT wrote:I am not well versed in this stuff, but once you download an unknown app on your phone can these people download something else on your phone ...like a virus that allows access to the data in the phone?
Really depends on what you are downloading, where you got it, what type of phone you have and what type of security software.
Related more for Google apps since that is what I use, each time you install an app, it provides you a list of what permissions it needs. If you are using Android, you really should look at that list and think about what they are asking permission for before authorizing. Just as important, you need to watch when apps update since many times they then ask for more permissions. The biggest problem with permissions is they are not detailed enough many times giving much more access than they actually need.
This is why I use a security program which can prevent an app from doing things I don't think it should be able to do. Might be that the app needs those things and if I don't trust it, I just don't use it. The security software also keeps a list of what an app has done. Example a flashlight app doesn't need access to the Internet, my contacts, ability to send texts etc.. its just a flashlight app. So most apps like that are locked down to not allow those. Each new app I add is blocked for everything and the security app shows me what they are trying to gain access to. I can then choose to allow access to just block that part.
A great example is Facebook. I have it on my phone but it has next to no access to do much of anything other than be Facebook. No access to my storage, contacts, texting etc... So if they decide to start playing in areas they haven't before, it is blocked (they have done this many times).
Typically software obtained from outside sources (away from Apple Store and Google Play) have a much higher risk of being insecure, but even apps from normal sources can have unknown issues.