Hello folks, within the effort to provide an implementation for some task implying from my daily job recently I started to face the following question related with auditd - how to write audit rules in most effective way. I am mainly interested if there's some comparison / research wrt to if there's is some performance penalty when (syscall, but in general case doesn't need to be limited to syscall calls) audit rules are created in the way having just one syscall rule (one -S argument is provided per audit rule) versus the case when there are more (compatible) -S arguments provided simultaneously in the particular audit.rules row? To provide an example, let's suppose the *chown category of rules: * the "all-in-one" case: -a always,exit -F arch=b32 -S chown -S fchown -S fchownat -S lchown -F auid>=500 -F auid!=4294967295 -k perm_mod vs * the "one-rule-per-one-row" case: -a always,exit -F arch=b32 -S chown -F auid>=500 -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S fchown -F auid>=500 -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S fchownat -F auid>=500 -F auid!=4294967295 -k perm_mod -a always,exit -F arch=b32 -S lchown -F auid>=500 -F auid!=4294967295 -k perm_mod Does the fact how the -S arguments are layered across the /etc/audit/audit.rules file (IOW if being provided within one row or spread within multiple rows) have some (negative) impact on the audit system's efficiency? [*] If so, is there some way how to measure the performance penalty in the second case? Thank you for your time & possible hints in advance. Regards, Jan. -- Jan iankko Lieskovsky / Red Hat Security Technologies Team [*] Not familiar with audit internals, but translating the request to log / audit the event of particular system call occurrence from the Linux kernel PoV's it looks this might correspond to the problem of searching for a key / value in the hash table (having particular system call occurred, insert new entry under particular hash table's field taking -k keyname argument as the hash table key). If this analogy is at least a bit appropriate, the all -S's arguments case above would correspond to a hash table having just one value for each key, while separating the desired -S arguments into multiple rows would mean to have a hash table where one key (-k keyname) would have bucket containing multiple values (e.g. array of them). In this case to locate the particular value would mean to locate the bucket in the hash table & then subsequently yet locate the proper value in that array of items (which seems to be more time / operation expensive than the case of one rule having multiple -S arguments). Thus could audit upstream clarify, if there's some performance penalty in the case of multiple -S being split / spread across multiple rules?