If you are running Suricata in IDS mode, it will generate alerts based on rules, but won’t drop the traffic (if you want malicious traffic to be dropped, consider the IPS mode - but that depends on the network setup you have, to really work);
If you want to capture the malicious traffic if certain alerts happen, the released Suricata versions don’t have that capability as of yet. But Conditional PCAP logging is one of the new features for Suricata 7, which should be released within a few months.
Mr Éric Leblond is the contributor for this addition. See his presentation during SuriCon2021: