[New Rule] Modification of WDigest Security Provider (#883)

* Create credential_access_mod_wdigest_security_provider.toml

* syntax tweaks

rules/windows/credential_access_mod_wdigest_security_provider.toml

@@ -0,0 +1,53 @@
+[metadata]
+creation_date = "2021/01/19"
+maturity = "production"
+updated_date = "2021/01/19"
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies attempts to modify the WDigest security provider in the registry to force the user's password to be stored in
+clear text in memory. This behavior can be indicative of an adversary attempting to weaken the security configuration of
+an endpoint. Once the UseLogonCredential value is modified, the adversary may attempt to dump clear text passwords from
+memory.
+"""
+from = "now-9m"
+index = ["winlogbeat-*", "logs-endpoint.events.*"]
+language = "eql"
+license = "Elastic License"
+name = "Modification of WDigest Security Provider"
+references = [
+    "https://www.csoonline.com/article/3438824/how-to-detect-and-halt-credential-theft-via-windows-wdigest.html",
+    "https://www.praetorian.com/blog/mitigating-mimikatz-wdigest-cleartext-credential-theft?edition=2019",
+]
+risk_score = 73
+rule_id = "d703a5af-d5b0-43bd-8ddb-7a5d500b7da5"
+severity = "high"
+tags = ["Elastic", "Host", "Windows", "Threat Detection", "Credential Access"]
+type = "eql"
+
+query = '''
+registry where event.type in ("creation", "change") and
+  registry.path:"HKLM\\SYSTEM\\*ControlSet*\\Control\\SecurityProviders\\WDigest\\UseLogonCredential" and
+  registry.data.strings:"1"
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1003"
+name = "OS Credential Dumping"
+reference = "https://attack.mitre.org/techniques/T1003/"
+[[rule.threat.technique.subtechnique]]
+id = "T1003.001"
+name = "LSASS Memory"
+reference = "https://attack.mitre.org/techniques/T1003/001/"
+
+
+
+[rule.threat.tactic]
+id = "TA0006"
+name = "Credential Access"
+reference = "https://attack.mitre.org/tactics/TA0006/"
+