diff --git a/prospector/llm/llm_service.py b/prospector/llm/llm_service.py
index cbc4e69e4..685bf79a0 100644
--- a/prospector/llm/llm_service.py
+++ b/prospector/llm/llm_service.py
@@ -3,9 +3,11 @@
 import validators
 from langchain_core.language_models.llms import LLM
 from langchain_core.output_parsers import StrOutputParser
+from requests import HTTPError
 
 from llm.instantiation import create_model_instance
-from llm.prompts import prompt_best_guess
+from llm.prompts.classify_commit import zero_shot as cc_zero_shot
+from llm.prompts.get_repository_url import prompt_best_guess
 from log.logger import logger
 from util.config_parser import LLMServiceConfig
 from util.singleton import Singleton
@@ -74,3 +76,53 @@ def get_repository_url(self, advisory_description, advisory_references) -> str:
             raise RuntimeError(f"Prompt-model chain could not be invoked: {e}")
 
         return url
+
+    def classify_commit(
+        self, diff: str, repository_name: str, commit_message: str
+    ) -> bool:
+        """Ask an LLM whether a commit is security relevant or not. The response will be either True or False.
+
+        Args:
+            candidate (Commit): The commit to input into the LLM
+
+        Returns:
+            True if the commit is deemed security relevant, False if not.
+
+        Raises:
+            ValueError if there is an error in the model invocation or the response was not valid.
+        """
+        try:
+            chain = cc_zero_shot | self.model | StrOutputParser()
+
+            is_relevant = chain.invoke(
+                {
+                    "diff": diff,
+                    "repository_name": repository_name,
+                    "commit_message": commit_message,
+                }
+            )
+            logger.info(f"LLM returned is_relevant={is_relevant}")
+
+        except HTTPError as e:
+            # if the diff is too big, a 400 error is returned -> silently ignore by returning False for this commit
+            status_code = e.response.status_code
+            if status_code == 400:
+                return False
+            raise RuntimeError(f"Prompt-model chain could not be invoked: {e}")
+        except Exception as e:
+            raise RuntimeError(f"Prompt-model chain could not be invoked: {e}")
+
+        if is_relevant in [
+            "True",
+            "ANSWER:True",
+            "```ANSWER:True```",
+        ]:
+            return True
+        elif is_relevant in [
+            "False",
+            "ANSWER:False",
+            "```ANSWER:False```",
+        ]:
+            return False
+        else:
+            raise RuntimeError(f"The model returned an invalid response: {is_relevant}")
diff --git a/prospector/llm/prompts/classify_commit.py b/prospector/llm/prompts/classify_commit.py
new file mode 100644
index 000000000..80a99afe9
--- /dev/null
+++ b/prospector/llm/prompts/classify_commit.py
@@ -0,0 +1,16 @@
+from langchain.prompts import PromptTemplate
+
+zero_shot = PromptTemplate.from_template(
+    """Is the following commit security relevant or not?
+Please provide the output as a boolean value, either True or False.
+If it is security relevant just answer True otherwise answer False. Do not return anything else.
+
+To provide you with some context, the name of the repository is: {repository_name}, and the
+commit message is: {commit_message}.
+
+Finally, here is the diff of the commit:
+{diff}\n
+
+
+Your answer:\n"""
+)
diff --git a/prospector/llm/prompts.py b/prospector/llm/prompts/get_repository_url.py
similarity index 100%
rename from prospector/llm/prompts.py
rename to prospector/llm/prompts/get_repository_url.py
diff --git a/prospector/rules/rules.py b/prospector/rules/rules.py
index 80496c812..2ba5a16e9 100644
--- a/prospector/rules/rules.py
+++ b/prospector/rules/rules.py
@@ -413,6 +413,18 @@ def apply(self, candidate: Commit, advisory_record: AdvisoryRecord):
         return False
 
 
+class CommitIsSecurityRelevant(Rule):
+    """Matches commits that are deemed security relevant by the commit classification service."""
+
+    def apply(
+        self,
+        candidate: Commit,
+    ) -> bool:
+        return LLMService().classify_commit(
+            candidate.diff, candidate.repository, candidate.message
+        )
+
+
 RULES_PHASE_1: List[Rule] = [
     VulnIdInMessage("VULN_ID_IN_MESSAGE", 64),
     # CommitMentionedInAdv("COMMIT_IN_ADVISORY", 64),
@@ -433,4 +445,6 @@ def apply(self, candidate: Commit, advisory_record: AdvisoryRecord):
     CommitHasTwins("COMMIT_HAS_TWINS", 2),
 ]
 
-RULES_PHASE_2: List[Rule] = []
+RULES_PHASE_2: List[Rule] = [
+    CommitIsSecurityRelevant("COMMIT_IS_SECURITY_RELEVANT", 32)
+]
diff --git a/prospector/rules/rules_test.py b/prospector/rules/rules_test.py
index 230c351e0..93c246ef4 100644
--- a/prospector/rules/rules_test.py
+++ b/prospector/rules/rules_test.py
@@ -89,7 +89,9 @@ def candidates():
             changed_files={
                 "core/src/main/java/org/apache/cxf/workqueue/AutomaticWorkQueueImpl.java"
             },
-            minhash=get_encoded_minhash(get_msg("Insecure deserialization", 50)),
+            minhash=get_encoded_minhash(
+                get_msg("Insecure deserialization", 50)
+            ),
         ),
         # TODO: Not matched by existing tests: GHSecurityAdvInMessage, ReferencesBug, ChangesRelevantCode, TwinMentionedInAdv, VulnIdInLinkedIssue, SecurityKeywordInLinkedGhIssue, SecurityKeywordInLinkedBug, CrossReferencedBug, CrossReferencedGh, CommitHasTwins, ChangesRelevantFiles, CommitMentionedInAdv, RelevantWordsInMessage
     ]
@@ -109,7 +111,9 @@ def advisory_record():
     )
 
 
-def test_apply_phase_1_rules(candidates: List[Commit], advisory_record: AdvisoryRecord):
+def test_apply_phase_1_rules(
+    candidates: List[Commit], advisory_record: AdvisoryRecord
+):
     annotated_candidates = apply_rules(
         candidates, advisory_record, enabled_rules=enabled_rules_from_config
     )
@@ -117,7 +121,9 @@ def test_apply_phase_1_rules(candidates: List[Commit], advisory_record: Advisory
     # Repo 5: Should match: AdvKeywordsInFiles, SecurityKeywordsInMsg, CommitMentionedInReference
     assert len(annotated_candidates[0].matched_rules) == 3
 
-    matched_rules_names = [item["id"] for item in annotated_candidates[0].matched_rules]
+    matched_rules_names = [
+        item["id"] for item in annotated_candidates[0].matched_rules
+    ]
     assert "ADV_KEYWORDS_IN_FILES" in matched_rules_names
     assert "COMMIT_IN_REFERENCE" in matched_rules_names
     assert "SEC_KEYWORDS_IN_MESSAGE" in matched_rules_names
@@ -125,21 +131,27 @@ def test_apply_phase_1_rules(candidates: List[Commit], advisory_record: Advisory
     # Repo 1: Should match: VulnIdInMessage, ReferencesGhIssue
     assert len(annotated_candidates[1].matched_rules) == 2
 
-    matched_rules_names = [item["id"] for item in annotated_candidates[1].matched_rules]
+    matched_rules_names = [
+        item["id"] for item in annotated_candidates[1].matched_rules
+    ]
     assert "VULN_ID_IN_MESSAGE" in matched_rules_names
     assert "GITHUB_ISSUE_IN_MESSAGE" in matched_rules_names
 
     # Repo 3: Should match: VulnIdInMessage, ReferencesGhIssue
     assert len(annotated_candidates[2].matched_rules) == 2
 
-    matched_rules_names = [item["id"] for item in annotated_candidates[2].matched_rules]
+    matched_rules_names = [
+        item["id"] for item in annotated_candidates[2].matched_rules
+    ]
     assert "VULN_ID_IN_MESSAGE" in matched_rules_names
     assert "GITHUB_ISSUE_IN_MESSAGE" in matched_rules_names
 
     # Repo 4: Should match: SecurityKeywordsInMsg
     assert len(annotated_candidates[3].matched_rules) == 1
 
-    matched_rules_names = [item["id"] for item in annotated_candidates[3].matched_rules]
+    matched_rules_names = [
+        item["id"] for item in annotated_candidates[3].matched_rules
+    ]
     assert "SEC_KEYWORDS_IN_MESSAGE" in matched_rules_names
 
     # Repo 2: Matches nothing