Router logs interpretation

[#1]

Can someone help identify what these mean in the router log.

[Site blocked: ocsp2.globalsign.com]

and [Site blocked: crl.globalsign.com]

[Self2WAN ICMP type b Detected!] To prevent from revealing router's activity, this packet is dropped!

[DOS Attack] : 1 [ACK Scan] packets detected in last 20 seconds, source ip [185.21.217.54] 

thanks

[#2]

I see no reason for the blocked URL's (I can get to the site in question), the ICMP is being blocked for trying to establish if there is anything listening on your IP address and something is trying to get into your router with the DOS attack, both can be ignored because the router is taking care of it.  All good