ISC Network Security · Updated November 2026
IDS or IPS: Does the System Only Detect or Also Block?
IDS primarily detects suspicious activity. IPS can actively block it.
IDS
An Intrusion Detection System primarily monitors and identifies suspicious activity, generating alerts and logs for investigation.
IPS
An Intrusion Prevention System can actively block or prevent malicious traffic under configured rules.
Tradeoff
Blocking creates availability risk when false positives interrupt legitimate connections.
The takeaway
IDS tells you something suspicious happened. IPS can actively stop it.
Related Summit guides
FAQ
Does IDS primarily block traffic?
No.
Can IPS create availability risk from false positives?
Yes.
Are IDS and IPS preventive or detective?
IDS is primarily detective; IPS includes preventive functionality.