Hi!
A have RB951G-2HnD. It was running on RouterOS 6.0 from the date of release with no changes in configuration and all was fine, until I added some new filters in firewall that block ddos. Just three. And my mikrotik went broken! Firewall started to show huge statistical numbers and all 56 policies stoped working at all with no logic.
So I upgraded to 6.1 and nothing gets fixed. Then I installed virtual machine with x86 RouterOS v6.1, and added those 3 policies in firewall/filter. And vuala! I broke it.
So, you can do it by your self on your borads I think, but DO A BACKUP FIRST! Enter this in terminal:
/ip firewall filter
add action=drop chain=ddos-check comment="DDos Prevention" protocol=tcp \
src-address-list=brute_force_list
add action=add-src-to-address-list address-list=brute_force_list \
address-list-timeout=5s chain=ddos-check connection-state=new dst-limit=\
120/1m,0,src-address/0ms protocol=tcp
add action=jump chain=forward comment="Check if is ddos attack and block" \
connection-state=new jump-target=ddos-check