The correct answer is B. in props.conf:
[identity]
SEDCMD-redact_pw = s/password=([^,|/s]+)/ ####REACTED####/g
According to the Splunk documentation1, to redact sensitive data from raw events, you need to use the SEDCMD attribute in the props.conf file. The SEDCMD attribute applies a sed expression to the raw data before indexing. The sed expression can use the s command to replace a pattern with a substitution string. For example, the following sed expression replaces any occurrence of password= followed by any characters until a comma, whitespace, or slash with ####REACTED####:
s/password=([^,|/s]+)/ ####REACTED####/g
The g flag at the end means that the replacement is applied globally, not just to the first match.
Option A is incorrect because it uses the REGEX attribute instead of the SEDCMD attribute. The REGEX attribute is used to extract fields from events, not to modify them.
Option C is incorrect because it uses the transforms.conf file instead of the props.conf file. The transforms.conf file is used to define transformations that can be applied to fields or events, such as lookups, evaluations, or replacements. However, these transformations are applied after indexing, not before.
Option D is incorrect because it uses both the wrong attribute and the wrong file. There is no REGEX-redact_pw attribute in the transforms.conf file.
References: 1: Redact data from events - Splunk Documentation