One easy way to tell if you are accidentally connected to a Pineapple type device instead of the actual network is by going to a secure https webpage. When doing that you would get a warning about the certificate not matching if you are connected to a Pineapple device. If you do not get a warning and the web page loads properly with the certificate then you should be fine.
Regarding the dates on your file. The download date will always be different than the .app's creation date. The .app's creation date is typically when the application was compiled if I recall correctly.
Your whole situation is basically the do's and dont's of connecting to an unsecured/uncontrolled wifi network. Basic security hygiene is best n that type of environment.
1. Make sure your computer is completely up to date and that your firewall and any other AV protection products are enabled.
2. Do as little as possible, avoid banking and other credentialed sites if possible although technically they should be https
3. If you don't want the network to see all of the websites you visit etc then I'd suggest using TOR or a VPN solution to hide/encrypt that.
Adam R MS | CISSP, CISM, VCP, MCITP, CCNP, ITILv3, CMNO
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