8.8. Integer Keywords

Many keywords will match on an integer value on the network traffic. These are unsigned integers that can be 8, 16, 32 or 64 bits.

Simple example:

bsize:integer value;

The integer value can be written as base-10 like 100 or as an hexadecimal value like 0x64.

The most direct example is to match for equality, but there are different modes.

8.8.1. Comparison modes

Integers can be matched for * Equality * Inequality * Greater than * Less than * Range * Negated range * Bitmask * Negated Bitmask

Note

Comparisons are strict by default. Ranges are thus exclusive. That means a range between 1 and 4 will match 2 and 3, but neither 1 nor 4. Negated range !1-4 will match for 1 or below and for 4 or above.

Examples:

bsize:19; # equality
bsize:=0x13; # equality
bsize:!0x14; # inequality
bsize:!=20; # inequality
bsize:>21; # greater than
bsize:>=21; # greater than or equal
bsize:<22; # lesser than
bsize:<=22; # lesser than or equal
bsize:19-22; # range between value1 and value2
bsize:!19-22; # negated range between value1 and value2
bsize:&0xc0=0x80; # bitmask mask is compared to value for equality
bsize:&0xc0!=0; # bitmask mask is compared to value for inequality

8.8.2. Enumerations

Some integers on the wire represent an enumeration, that is, some values have a string/meaning associated to it. Rules can be written using one of these strings to check for equality. This is meant to make rules more human-readable and equivalent for matching.

Examples:

websocket.opcode:text;
websocket.opcode:1; # behaves the same

8.8.3. Bitmasks

Some integers on the wire represent multiple bits. Some of these bits have a string/meaning associated to it. Rules can be written using a list (comma-separated) of these strings, where each item can be negated.

There is no right shift for trailing zeros applied here (even if there is one for byte_test and byte_math). That means a rule with websocket.flags:&0xc0=2 will be rejected as invalid as it can never match.

Examples:

websocket.flags:fin,!comp;
websocket.flags:&0xc0=0x80; # behaves the same