Is the message "You must change your passcode within 60 minutes" valid / non-malware?
This message is the case when either:


Your device is enrolled under MDM and after deployment it will display something like image below.(https://www.apple.com/iphone/business/it/management.html)
Your passcode is too obvious and needs to be changed
Microsoft Exchange can force a passcode on your iPhone.




Obvious codes start with the following numbers: 


196* 
197*
198* 
199*
200*
201*


But also include:


1234
0000 (or any 4 same number combination)
0001 or 0010 or 0100 or 1000 (or any number with this pattern)
1379
2580
2468