diff --git a/analyzers/ProofPoint/proofpoint_lookup.py b/analyzers/ProofPoint/proofpoint_lookup.py
index 25264ba6a..04f476eae 100755
--- a/analyzers/ProofPoint/proofpoint_lookup.py
+++ b/analyzers/ProofPoint/proofpoint_lookup.py
@@ -63,7 +63,9 @@ def run(self):
 				if self.data_type == 'file':
 					filename = self.get_param('attachment.name', 'noname.ext')
 					filepath = self.get_param('file', None, 'File is missing')
-					sha256 = hashlib.sha256(open(filepath, 'r').read()).hexdigest()
+					with open(filepath, "rb") as f:
+						digest = hashlib.file_digest(f, "sha256")
+					sha256 = digest.hexdigest()
 				elif self.data_type == 'hash' and len(self.get_data()) == 64:
 					sha256 = self.get_data()
 				else: