diff --git a/pre_commit_hooks/detect_aws_credentials.py b/pre_commit_hooks/detect_aws_credentials.py
index 9dda217..420333d 100644
--- a/pre_commit_hooks/detect_aws_credentials.py
+++ b/pre_commit_hooks/detect_aws_credentials.py
@@ -7,62 +7,118 @@
 from six.moves import configparser
 
 
-def get_your_keys(credentials_file):
-    """reads the secret keys in your credentials file in order to be able to
-    look for them in the submitted code.
+def get_aws_credential_files_from_env():
+    """Extract credential file paths from environment variables."""
+    files = set()
+    for env_var in {'AWS_CREDENTIAL_FILE', 'AWS_SHARED_CREDENTIALS_FILE',
+                    'BOTO_CONFIG'}:
+        try:
+            files.add(os.environ[env_var])
+        except KeyError:
+            pass
+    return files
+
+
+def get_aws_secrets_from_env():
+    """Extract AWS secrets from environment variables."""
+    keys = set()
+    for env_var in {'AWS_SECRET_ACCESS_KEY', 'AWS_SECURITY_TOKEN',
+                    'AWS_SESSION_TOKEN'}:
+        try:
+            keys.add(os.environ[env_var])
+        except KeyError:
+            pass
+    return keys
+
+
+def get_aws_secrets_from_file(credentials_file):
+    """Extract AWS secrets from configuration files.
+
+    Read an ini-style configuration file and return a set with all found AWS
+    secret access keys.
     """
     aws_credentials_file_path = os.path.expanduser(credentials_file)
     if not os.path.exists(aws_credentials_file_path):
-        return None
+        return set()
 
     parser = configparser.ConfigParser()
-    parser.read(aws_credentials_file_path)
+    try:
+        parser.read(aws_credentials_file_path)
+    except configparser.MissingSectionHeaderError:
+        return set()
 
     keys = set()
     for section in parser.sections():
-        keys.add(parser.get(section, 'aws_secret_access_key'))
+        for var in {'aws_secret_access_key', 'aws_security_token',
+                    'aws_session_token'}:
+            try:
+                keys.add(parser.get(section, var))
+            except configparser.NoOptionError:
+                pass
     return keys
 
 
 def check_file_for_aws_keys(filenames, keys):
+    """Check if files contain AWS secrets.
+
+    Return a list of all files containing AWS secrets and keys found, with all
+    but the first four characters obfuscated to ease debugging.
+    """
     bad_files = []
 
     for filename in filenames:
         with open(filename, 'r') as content:
             text_body = content.read()
-            if any(key in text_body for key in keys):
-                # naively match the entire file, low chance of incorrect collision
-                bad_files.append(filename)
-
+            for key in keys:
+                # naively match the entire file, low chance of incorrect
+                # collision
+                if key in text_body:
+                    bad_files.append({'filename': filename,
+                                      'key': key[:4].ljust(32, str('*'))})
     return bad_files
 
 
 def main(argv=None):
     parser = argparse.ArgumentParser()
-    parser.add_argument('filenames', nargs='*', help='Filenames to run')
+    parser.add_argument('filenames', nargs='+', help='Filenames to run')
     parser.add_argument(
         '--credentials-file',
-        default='~/.aws/credentials',
+        dest='credential_files',
+        action='append',
+        default=['~/.aws/config', '~/.aws/credentials', '/etc/boto.cfg',
+                 '~/.boto'],
         help=(
-            'location of aws credentials file from which to get the secret '
-            "keys we're looking for"
-        ),
+            'Location of additional AWS credential files from which to get '
+            'secret keys from'
+        )
     )
     args = parser.parse_args(argv)
-    keys = get_your_keys(args.credentials_file)
+
+    credential_files = set(args.credential_files)
+
+    # Add the credentials files configured via environment variables to the set
+    # of files to to gather AWS secrets from.
+    credential_files |= get_aws_credential_files_from_env()
+
+    keys = set()
+    for credential_file in credential_files:
+        keys |= get_aws_secrets_from_file(credential_file)
+
+    # Secrets might be part of environment variables, so add such secrets to
+    # the set of keys.
+    keys |= get_aws_secrets_from_env()
+
     if not keys:
-        print(
-            'No aws keys were configured at {0}\n'
-            'Configure them with --credentials-file'.format(
-                args.credentials_file,
-            ),
-        )
+        print('No AWS keys were found in the configured credential files and '
+              'environment variables.\nPlease ensure you have the correct '
+              'setting for --credentials-file')
         return 2
 
     bad_filenames = check_file_for_aws_keys(args.filenames, keys)
     if bad_filenames:
         for bad_file in bad_filenames:
-            print('AWS secret key found: {0}'.format(bad_file))
+            print('AWS secret found in {filename}: {key}'.format(
+                **bad_file))
         return 1
     else:
         return 0