input.json

{
  "ip": "192.168.1.1",
  "message": "Hello peter@gmail.com.  You signed up with card 1234-1234-1234-1234. Your home folder is C:\\Users\\peter. Look at our compliance from 127.0.0.1",
  "extra": {
    "foo": 42,
    "bar": true
  }
}

postprocessing.json

{
  "ip": null,
  "message": "Hello *****@*****.***.  You signed up with card ****-****-****-1234. Your home folder is C:\\Users\\[username] Look at our compliance from 5A2DF387CD660E9F3E0AB20F9E7805450D56C5DACE9B959FC620C336E2B5D09A",
  "extra": {
    "foo": null,
    "bar": true
  },
  "metadata": {
    "ip": {
      "": {
        "remarks": [
          [["remove_ip", "IP address removed"]]
        ]
      }
    },
    "message": {
      "": {
        "remarks": [
          [["email_address", "potential email address"], [6, 21]],
          [["creditcard_number", "creditcard number"], [48, 67]],
          [["path_username", "username in path"], [98, 108]],
          [["hash_ip", "IP address hashed"], [137, 201]]
        ],
        "original_length": 142
      }
    },
    "extra": {
      "foo": {
        "": {
          "remarks": [
            [["remove_foo"]]
          ]
        }
      }
    }
  }
}

rules.json

{
  "rules": {
    "creditcard_numbers": {
      "note": "creditcard number",
      "pattern": "\\d{4}[- ]?\\d{4,6}[- ]?\\d{4,5}(?:[- ]?\\d{4})",
      "type": "pattern",
      "replace_with": {
        "mask_range": [
          6,
          -4
        ],
        "mask_with_char": "*",
        "chars_to_ignore": "- "
      }
    },
    "password_pairs": {
      "note": "password",
      "type": "remove_pair_value",
      "key_pattern": "password|pw|pword|pwd",
      "replace_with": {
        "new_value": "[password]"
      }
    },
    "email_address": {
      "note": "potential email address",
      "pattern": "[a-z0-9!#$%&'*+/=?^_`{|}~.-]+@[a-z0-9-]+(\\.[a-z0-9-]+)*",
      "type": "pattern",
      "replace_with": {
        "mask_with_char": "*",
        "chars_to_ignore": "@."
      }
    },
    "path_username": {
      "note": "username in path",
      "pattern": "(?:\b[a-zA-Z]:)?(?:[/\\\\](users|home)[/\\\\])([^/\\\\]+)",
      "replace_with": {
        "new_value": "[username]"
      },
      "type": "pattern",
      "replace_groups": [
        1
      ]
    },
    "ipv4": {
      "note": "ip address",
      "pattern": "\\b((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\b",
      "type": "pattern",
      "replace_with": {
        "mask_with_char": "*",
        "chars_to_ignore": "."
      }
    }
  },
  "applications": {
    "freeform": [
      "path_username",
      "creditcard_numbers",
      "email_address",
      "ipv4"
    ],
    "databag": [
      "path_username",
      "creditcard_numbers",
      "email_address",
      "ipv4",
      "password_pairs"
    ]
  }
}