If your firewall drops the packages (ZA does this when internet security level set to "high") you don't have to worry about those warnings, if you see many times the same IP, you could contact the IP adress owner. For the IP you mentioned 18.104.22.168 :
4D communications (NETBLK-4DCOMM)
3350 Sports Arena Blvd. Suite K
San Diego, CA 92110
Netblock: 22.214.171.124 - 126.96.36.199
Colina, Jose E (JEC3-ARIN) email@example.com
(619)523-2721 Ext. 324 (FAX) 619-521-2614
About your first alerts:
Pac-West Telecomm, INC. (NETBLK-MDSG-PACWEST)
1776 W. March Lane, Suite 250
Stockton, CA 95207
Netblock: 188.8.131.52 - 184.108.40.206
Pac-West Telecomm Inc. (ZP86-ARIN) firstname.lastname@example.org
Perhaps this is your own ISP ?
And like said before by iNViCTuS the destination is in the multicast / netcast adress range. NET-MCAST-NET, so it is not traffic targeted at your box only.
It could be some router problem by an ISP or ZA acting to sensitive.
Some ISP's also perform a check on their networks (like a ping) everytime you log in or they could be doing this at certain or at random times.
I believe this info was alos provided in the above posts, but this is a sort of summary of the possibilities and solutions mentioned above. I hope this helped