Common: Allow '.' characters in Event tags

The MITRE ATT&CK framework identifies subtechniques by using a '.' to
separate the technique ID from the subtechnique ID. For example, the
technique "Defacement" has the ID T1491, whereas the subtechnique
"Internal Defacement" has the ID T1491.001.

Allowing '.' characters in tags allows us to specify MITRE ATT&CK
subtechniques without performing any translation.

PR #3676

CHANGELOG.md

@@ -23,7 +23,7 @@ Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Changed
 - Plugin source is now gzipped. #3392
-- Allowed characters in Agent event tags. #3399
+- Allowed characters in Agent event tags. #3399, #3676
 - Hard-coded Log4Shell exploiter to a plugin. #3388
 - Hard-coded SSH exploiter to a plugin. #3170
 - Identities and secrets can be associated when configuring credentials in the

monkey/common/agent_events/abstract_agent_event.py

@@ -8,7 +8,7 @@
 from common.base_models import InfectionMonkeyBaseModel, InfectionMonkeyModelConfig
 from common.types import AgentID, MachineID
 
-EVENT_TAG_REGEX = r"^[a-zA-Z0-9_-]+$"
+EVENT_TAG_REGEX = r"^[a-zA-Z0-9._-]+$"
 
 
 class AgentEventTag(ConstrainedStr):