Install SquidBlacklist Malicious IP scripts as sort of described at http://blog.squidblacklist.org/?p=297

Script.installSquidBlacklistScriptsMalicious.rsc

# Script which will download the SquidBlacklistMalicious list as a text file
/system script add name="Download_SquidBlacklistMalicious" source={
  /tool fetch url="http://www.squidblacklist.org/downloads/drop.malicious.rsc" mode=http;
  :log info "Downloaded drop.malicious.rsc from squidblacklist.org";
}

# Script which will Remove old SquidBlacklistMalicious list and add new one
/system script add name="Replace_SquidBlacklistMalicious" source={
  /system logging disable 0
  /ip firewall address-list remove [find where comment="SquidBlacklistMalicious"]
  /import file-name=drop.malicious.rsc;
  /system logging enable 0
  :log info "Removed old SquidBlacklistMalicious records and imported new list";
}

# Schedule the download and application of the SquidBlacklistMalicious list
/system scheduler add comment="Download SquidBlacklistMalicious list" interval=3d \
  name="DownloadSquidBlacklistMaliciousList" on-event=Download_SquidBlacklistMalicious \
  start-date=jan/01/1970 start-time=04:26:52
/system scheduler add comment="Apply SquidBlacklistMalicious List" interval=3d \
  name="InstallSquidBlacklistMaliciousList" on-event=Replace_SquidBlacklistMalicious \
  start-date=jan/01/1970 start-time=04:31:52

# Install the firewall rules of the SquidBlacklistMalicious list
/ip firewall filter add chain=input src-address-list=drop.dshield action=drop log=yes log-prefix=drop.dshield
/ip firewall filter add chain=input src-address-list=drop.spamhaus1 action=drop log=yes log-prefix=drop.spamhaus1
/ip firewall filter add chain=input src-address-list=drop.spamhaus2 action=drop log=yes log-prefix=drop.spamhaus2
/ip firewall filter add chain=input dst-address-list=drop.dshield action=drop log=yes log-prefix=drop.dshield
/ip firewall filter add chain=input dst-address-list=drop.spamhaus1 action=drop log=yes log-prefix=drop.spamhaus1
/ip firewall filter add chain=input dst-address-list=drop.spamhaus2 action=drop log=yes log-prefix=drop.spamhaus2