diff --git a/crates/ruff/src/rules/flake8_bandit/rules/hashlib_insecure_hash_functions.rs b/crates/ruff/src/rules/flake8_bandit/rules/hashlib_insecure_hash_functions.rs
index 1e624cd5fa..91ee429343 100644
--- a/crates/ruff/src/rules/flake8_bandit/rules/hashlib_insecure_hash_functions.rs
+++ b/crates/ruff/src/rules/flake8_bandit/rules/hashlib_insecure_hash_functions.rs
@@ -1,8 +1,8 @@
-use rustpython_parser::ast::{self, Constant, Expr, Keyword, Ranged};
+use rustpython_parser::ast::{Expr, Keyword, Ranged};
 
 use ruff_diagnostics::{Diagnostic, Violation};
 use ruff_macros::{derive_message_formats, violation};
-use ruff_python_ast::helpers::SimpleCallArgs;
+use ruff_python_ast::helpers::{is_const_false, SimpleCallArgs};
 
 use crate::checkers::ast::Checker;
 
@@ -21,26 +21,6 @@ impl Violation for HashlibInsecureHashFunction {
     }
 }
 
-const WEAK_HASHES: [&str; 4] = ["md4", "md5", "sha", "sha1"];
-
-fn is_used_for_security(call_args: &SimpleCallArgs) -> bool {
-    match call_args.keyword_argument("usedforsecurity") {
-        Some(expr) => !matches!(
-            expr,
-            Expr::Constant(ast::ExprConstant {
-                value: Constant::Bool(false),
-                ..
-            })
-        ),
-        _ => true,
-    }
-}
-
-enum HashlibCall {
-    New,
-    WeakHash(&'static str),
-}
-
 /// S324
 pub(crate) fn hashlib_insecure_hash_functions(
     checker: &mut Checker,
@@ -51,15 +31,13 @@ pub(crate) fn hashlib_insecure_hash_functions(
     if let Some(hashlib_call) = checker
         .semantic()
         .resolve_call_path(func)
-        .and_then(|call_path| {
-            if matches!(call_path.as_slice(), ["hashlib", "new"]) {
-                Some(HashlibCall::New)
-            } else {
-                WEAK_HASHES
-                    .iter()
-                    .find(|hash| call_path.as_slice() == ["hashlib", hash])
-                    .map(|hash| HashlibCall::WeakHash(hash))
-            }
+        .and_then(|call_path| match call_path.as_slice() {
+            ["hashlib", "new"] => Some(HashlibCall::New),
+            ["hashlib", "md4"] => Some(HashlibCall::WeakHash("md4")),
+            ["hashlib", "md5"] => Some(HashlibCall::WeakHash("md5")),
+            ["hashlib", "sha"] => Some(HashlibCall::WeakHash("sha")),
+            ["hashlib", "sha1"] => Some(HashlibCall::WeakHash("sha1")),
+            _ => None,
         })
     {
         match hashlib_call {
@@ -72,7 +50,12 @@ pub(crate) fn hashlib_insecure_hash_functions(
 
                 if let Some(name_arg) = call_args.argument("name", 0) {
                     if let Some(hash_func_name) = string_literal(name_arg) {
-                        if WEAK_HASHES.contains(&hash_func_name.to_lowercase().as_str()) {
+                        // `hashlib.new` accepts both lowercase and uppercase names for hash
+                        // functions.
+                        if matches!(
+                            hash_func_name,
+                            "md4" | "md5" | "sha" | "sha1" | "MD4" | "MD5" | "SHA" | "SHA1"
+                        ) {
                             checker.diagnostics.push(Diagnostic::new(
                                 HashlibInsecureHashFunction {
                                     string: hash_func_name.to_string(),
@@ -100,3 +83,15 @@ pub(crate) fn hashlib_insecure_hash_functions(
         }
     }
 }
+
+fn is_used_for_security(call_args: &SimpleCallArgs) -> bool {
+    match call_args.keyword_argument("usedforsecurity") {
+        Some(expr) => !is_const_false(expr),
+        _ => true,
+    }
+}
+
+enum HashlibCall {
+    New,
+    WeakHash(&'static str),
+}
diff --git a/crates/ruff_python_ast/src/helpers.rs b/crates/ruff_python_ast/src/helpers.rs
index 38b750d00d..f8ab144d28 100644
--- a/crates/ruff_python_ast/src/helpers.rs
+++ b/crates/ruff_python_ast/src/helpers.rs
@@ -634,6 +634,18 @@ pub const fn is_const_true(expr: &Expr) -> bool {
     )
 }
 
+/// Return `true` if an [`Expr`] is `False`.
+pub const fn is_const_false(expr: &Expr) -> bool {
+    matches!(
+        expr,
+        Expr::Constant(ast::ExprConstant {
+            value: Constant::Bool(false),
+            kind: None,
+            ..
+        }),
+    )
+}
+
 /// Return `true` if a keyword argument is present with a non-`None` value.
 pub fn has_non_none_keyword(keywords: &[Keyword], keyword: &str) -> bool {
     find_keyword(keywords, keyword).map_or(false, |keyword| {