Methods / Compare / SYN Flood vs ACK Flood
Comparison
SYN Flood vs ACK Flood
Both are Layer-4 TCP floods, but they pressure different parts of the stack. Here is how they differ and when to reach for each.
SYN
L4- →Half-open connections
- →Exhausts the SYN backlog
- →Spoofable source
- →SYN-cookie pressure
- ★Best for: backlog and SYN-cookie tuning
View SYN →
ACK
L4- →Out-of-state packets
- →Burns connection-tracking CPU
- →Slips past stateless filters
- →Pure volumetric load
- ★Best for: conntrack and ACL validation
View ACK →
The verdict
Use SYN to validate backlog sizing and SYN-cookie configuration; use ACK to validate connection-tracking capacity and out-of-state drop rules.
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