diff --git a/README.md b/README.md
index 317a83c..19b0c20 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# phpstan-rules
+# PHPStan Rules
 Set of additional PHPStan rules
 
 - check if property and constant shouldn't be set as protected (when is not inherited or class is not abstract)
diff --git a/extension.neon b/extension.neon
new file mode 100644
index 0000000..3c6f403
--- /dev/null
+++ b/extension.neon
@@ -0,0 +1,13 @@
+services:
+	-
+	    class: PMarki\PHPStanRules\Rules\ConstRule
+	    tags:
+	        - phpstan.rules.rule
+	-
+	    class: PMarki\PHPStanRules\Rules\ProtectedMethodRule
+	    tags:
+	        - phpstan.rules.rule
+	-
+	    class: PMarki\PHPStanRules\Rules\ProtectedPropertyRule
+	    tags:
+	        - phpstan.rules.rule
diff --git a/src/Rules/ProtectedMethodRule.php b/src/Rules/ProtectedMethodRule.php
new file mode 100644
index 0000000..bcf45b5
--- /dev/null
+++ b/src/Rules/ProtectedMethodRule.php
@@ -0,0 +1,78 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PMarki\PHPStanRules\Rules;
+
+use PhpParser\Node;
+use PhpParser\Node\Stmt\ClassMethod;
+use PHPStan\Analyser\Scope;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+
+/**
+ * Reports an error when a method is protected in a non-abstract class unless it is inherited from a parent class.
+ *
+ * @implements Rule<ClassMethod>
+ */
+class ProtectedMethodRule implements Rule
+{
+    public function getNodeType(): string
+    {
+        return ClassMethod::class;
+    }
+
+    /**
+     * @return array<int, \PHPStan\Rules\RuleError>
+     */
+    public function processNode(Node $node, Scope $scope): array
+    {
+        if (!$node instanceof ClassMethod) {
+            return [];
+        }
+
+        $errors = [];
+        $methodName = $node->name->toString();
+        if ($this->methodInherited($methodName, $scope)) {
+            return [];
+        }
+
+        if (\str_starts_with($methodName, '_') && !\str_starts_with($methodName, '__')) {
+            $errors[] = RuleErrorBuilder::message("Method {$methodName}() must not start with underscore.")
+                ->identifier('extraMethodRules')
+                ->build();
+        }
+
+        if ($node->isProtected() && !$this->isInAbstractClass($scope)) {
+            $errors[] = RuleErrorBuilder::message("Method {$methodName}() should have private visibility.")
+                ->identifier('extraMethodRules')
+                ->tip("Protected methods can be used only in abstract classes or when inherited.")
+                ->build();
+        }
+
+        return $errors;
+    }
+
+    private function isInAbstractClass(Scope $scope): bool
+    {
+        $classReflection = $scope->getClassReflection();
+        return $classReflection === null || $classReflection->isAbstract();
+    }
+
+    private function methodInherited(string $methodName, Scope $scope): bool
+    {
+        $classReflection = $scope->getClassReflection();
+
+        foreach (\array_merge($classReflection->getParents(), $classReflection->getInterfaces()) as $ancestor) {
+            if ($ancestor->hasMethod($methodName)) {
+                $method = $ancestor->getMethod($methodName, $scope);
+
+                if (!$method->isPrivate()) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+}
diff --git a/tests/ProtectedMethodRuleTest.php b/tests/ProtectedMethodRuleTest.php
new file mode 100644
index 0000000..e62ba02
--- /dev/null
+++ b/tests/ProtectedMethodRuleTest.php
@@ -0,0 +1,95 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PMarki\PHPStanRules\Tests;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+use PMarki\PHPStanRules\Rules\ProtectedMethodRule;
+
+class ProtectedMethodRuleTest extends RuleTestCase
+{
+    private const TIP = "\n    💡 Protected methods can be used only in abstract classes or when inherited.";
+
+    public function testNoAbstractClass(): void
+    {
+        $this->analyse(
+            [__DIR__ . '/fixtures/ProtectedMethodRule/NoAbstractClass.php'],
+            [
+                [
+                    'Method protectedMethod() should have private visibility.' . self::TIP,
+                    6,
+                ],
+                [
+                    'Method _underscore() must not start with underscore.',
+                    9,
+                ],
+                [
+                    'Method _underscoreProtected() must not start with underscore.',
+                    10,
+                ],
+                [
+                    'Method _underscoreProtected() should have private visibility.' . self::TIP,
+                    10,
+                ],
+            ],
+        );
+    }
+
+    public function testAbstractClass(): void
+    {
+        $this->analyse(
+            [__DIR__ . '/fixtures/ProtectedMethodRule/AbstractClass.php'],
+            [
+                [
+                    'Method _underscore() must not start with underscore.',
+                    9,
+                ],
+                [
+                    'Method _underscoreProtected() must not start with underscore.',
+                    10,
+                ],
+            ],
+        );
+    }
+
+    public function testChildClass(): void
+    {
+        $this->analyse(
+            [
+                __DIR__ . '/fixtures/ProtectedMethodRule/ChildClass.php',
+            ],
+            [
+                [
+                    'Method childMethod() should have private visibility.' . self::TIP,
+                    8,
+                ],
+                [
+                    'Method _underscore() must not start with underscore.',
+                    11,
+                ],
+            ],
+        );
+    }
+
+    public function testInterface(): void
+    {
+        $this->analyse(
+            [
+                __DIR__ . '/fixtures/ProtectedMethodRule/Interface.php',
+            ],
+            [
+                [
+                    'Method _underscoreProtected() must not start with underscore.',
+                    7,
+                ],
+            ],
+        );
+    }
+
+    protected function getRule(): Rule
+    {
+        return new ProtectedMethodRule();
+    }
+}
diff --git a/tests/fixtures/ProtectedMethodRule/AbstractClass.php b/tests/fixtures/ProtectedMethodRule/AbstractClass.php
new file mode 100644
index 0000000..8a1ff94
--- /dev/null
+++ b/tests/fixtures/ProtectedMethodRule/AbstractClass.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace MethodRules;
+
+abstract class AbstractClass {
+    protected function protectedMethod() {} // good
+    public function publicMethod() {} // good
+    private function privateMethod() {} // good
+    private function _underscore() {} // no underscore
+    protected function _underscoreProtected() {} // no underscore
+    public function __construct() {} // good
+}
diff --git a/tests/fixtures/ProtectedMethodRule/ChildClass.php b/tests/fixtures/ProtectedMethodRule/ChildClass.php
new file mode 100644
index 0000000..6d85b8a
--- /dev/null
+++ b/tests/fixtures/ProtectedMethodRule/ChildClass.php
@@ -0,0 +1,14 @@
+<?php
+
+namespace MethodRules;
+
+class ChildClass extends AbstractClass
+{
+    protected function protectedMethod() {} // good
+    protected function childMethod() {} // no inherited
+    public function publicMethod() {} // good
+    private function privateMethod() {} // good
+    private function _underscore() {} // no underscore
+    protected function _underscoreProtected() {} // good, inherited
+    public function __get($name) {} // good
+}
diff --git a/tests/fixtures/ProtectedMethodRule/Interface.php b/tests/fixtures/ProtectedMethodRule/Interface.php
new file mode 100644
index 0000000..065f094
--- /dev/null
+++ b/tests/fixtures/ProtectedMethodRule/Interface.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace MethodRules;
+
+interface Foo
+{
+    function _underscoreProtected(); // bad, no leading underscore
+}
+
+class ChildClass implements Foo
+{
+    public function _underscoreProtected() {} // good, inherited
+}
diff --git a/tests/fixtures/ProtectedMethodRule/NoAbstractClass.php b/tests/fixtures/ProtectedMethodRule/NoAbstractClass.php
new file mode 100644
index 0000000..2ff8f48
--- /dev/null
+++ b/tests/fixtures/ProtectedMethodRule/NoAbstractClass.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace MethodRules;
+
+class NoAbstractClass {
+    protected function protectedMethod() {} // bad
+    public function publicMethod() {} // good
+    private function privateMethod() {} // good
+    private function _underscore() {} // no underscore
+    protected function _underscoreProtected() {} // no underscore
+    public function __construct() {} // good
+}