Enterasys Intrusion Prevention System Manual page 166

Creating Custom Signatures
a{1,10}__b{1,10}__c{1,10}
3-24 Creating Network Sensor Signatures
Note: In general, if you know the exact format of the content you are trying to match (including the
proper number of spaces), use the Extended Pattern type. For any data that may be variable, use
PCRE. Strict content checks (of sufficient length) are generally more efficient than regular
expressions.