The hacker could have used the technique of manipulating white spaces in SQL queries to bypass signature detection. This technique involves inserting, removing, or replacing white spaces in SQL queries with other characters or symbols that are either ignored or interpreted as white spaces by the SQL engine, but not by the signature-based IDS. This way, the hacker can alter the appearance of the query and evade the pattern matching of the IDS, while preserving the functionality and logic of the query. For example, the hacker could replace the space character with a tab character, a newline character, a comment symbol, or a URL-encoded value, such as %2012.

The other options are not correct for the following reasons:

A. Utilizing the char encoding function to convert hexadecimal and decimal values into characters that pass-through SQL engine parsing: This option is not feasible because the char encoding function is not supported by all SQL engines, and it may not be able to convert all hexadecimal and decimal values into valid characters. Moreover, the char encoding function may not be able to bypass the signature detection of the IDS, as it may still match the keywords or syntax of the SQL query3.

B. Using the URL encoding method to replace characters with their ASCII codes in hexadecimal form: This option is not effective because the URL encoding method is not applicable to SQL queries, as it is designed for encoding special characters in URLs. The URL encoding method may not be able to replace all characters with their ASCII codes, and it may not be able to preserve the functionality and logic of the SQL query. Furthermore, the URL encoding method may not be able to evade the signature detection of the IDS, as it may still match the keywords or syntax of the SQL query4.

C. Implementing sophisticated matches such as “OR ‘john’ = john" in place of classical matches like “OR 1-1”: This option is not advanced because it is a common and basic SQL injection technique that does not involve any evasion or obfuscation. This technique involves injecting a logical expression that is always true, such as “OR ‘john’ = john” or “OR 1-1”, to bypass the authentication or authorization checks of the SQL query. However, this technique may not be able to bypass the signature detection of the IDS, as it may easily match the keywords or syntax of the SQL query.