A security analyst is reviewing a new IOC in which data is injected into an online process. The IOC shows the data injection could happen in the following ways:
• Five numerical digits followed by a dash, followed by four numerical digits; or
• Five numerical digits
When one of these IOCs is identified. the online process stops working. Which of the following regular expressions should be implemented in the NIPS?
The best regular expression to address the given IOC patterns is ^\d{5}(-\d{4})?$. This regular expression precisely matches the described formats: five numerical digits followed by an optional dash and four numerical digits, or just five numerical digits alone. '^' asserts the start of the string, '\d{5}' matches exactly five digits, '(-\d{4})?' optionally matches a dash followed by exactly four digits, and '$' asserts the end of the string. This ensures that the patterns described in the IOC are properly detected.
B - ^\d{5}(-\d{4})?$: Spend a few hours on https://regex101[.]com/ if you don't already know it. ^ - position at the start of the line \d - matches any digit [0-9] {5} - matches the previous token 5 times (in this case '\d' or any digit) ( ....)? - Capture group, includes a match on the first token (our 5 digits) and what's inside the (...). -\d{4} - a dash "-" followed by any 4 digits $ - position at the end of a line