360 security is part of Umi OS and don't contain any malware but such warning can be on because this app is not part of stock android and Umi OS is customised ROM based on Android 7.
You can deactivated 360 security in settings or flash Basic ROM without this app.
mspiderv replied at 2018-6-1 04:33
No you cant deactive it. Seishin send screenshot where you can cleary see, it is not possible to d ...
Flash the basic edition ROM to get rid of the 360 Security and other bloatware/adware apps. An update for the S2 Pro is in progress but you can instantly solve your issue by flashing this ROM.
Link: http://community.umidigi.com/thread-16944-1-1.html
You can anytime flash an official ROM to reinstate your warranty - a few clicks and a few minutes. Anyway a stock Android 8.1 upgrade will be released for the S2 Pro.