diff --git a/core-java-modules/core-java-security-manager/pom.xml b/core-java-modules/core-java-security-manager/pom.xml
new file mode 100644
index 0000000000..51d5e7d78f
--- /dev/null
+++ b/core-java-modules/core-java-security-manager/pom.xml
@@ -0,0 +1,34 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-security-manager</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <packaging>jar</packaging>
+    <name>core-java-security-manager</name>
+	
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+  
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+
+    </build>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+    </properties>
+</project>
diff --git a/core-java-modules/core-java-security-manager/src/main/java/com/baeldung/security/manager/CustomPermission.java b/core-java-modules/core-java-security-manager/src/main/java/com/baeldung/security/manager/CustomPermission.java
new file mode 100644
index 0000000000..5f9c43336f
--- /dev/null
+++ b/core-java-modules/core-java-security-manager/src/main/java/com/baeldung/security/manager/CustomPermission.java
@@ -0,0 +1,13 @@
+package com.baeldung.security.manager;
+
+import java.security.BasicPermission;
+
+public class CustomPermission extends BasicPermission {
+    public CustomPermission(String name) {
+        super(name);
+    }
+
+    public CustomPermission(String name, String actions) {
+        super(name, actions);
+    }
+}
diff --git a/core-java-modules/core-java-security-manager/src/main/java/com/baeldung/security/manager/Service.java b/core-java-modules/core-java-security-manager/src/main/java/com/baeldung/security/manager/Service.java
new file mode 100644
index 0000000000..1b9f14e3b8
--- /dev/null
+++ b/core-java-modules/core-java-security-manager/src/main/java/com/baeldung/security/manager/Service.java
@@ -0,0 +1,18 @@
+package com.baeldung.security.manager;
+
+public class Service {
+
+    public static final String OPERATION = "my-operation";
+
+    public void operation() {
+        SecurityManager securityManager = System.getSecurityManager();
+        if (securityManager != null) {
+            securityManager.checkPermission(new CustomPermission(OPERATION));
+        }
+        System.out.println("Operation is executed");
+    }
+
+    public static void main(String[] args) {
+        new Service().operation();
+    }
+}
diff --git a/core-java-modules/core-java-security-manager/src/test/java/com/baeldung/security/manager/SecurityManagerUnitTest.java b/core-java-modules/core-java-security-manager/src/test/java/com/baeldung/security/manager/SecurityManagerUnitTest.java
new file mode 100644
index 0000000000..a845f233b5
--- /dev/null
+++ b/core-java-modules/core-java-security-manager/src/test/java/com/baeldung/security/manager/SecurityManagerUnitTest.java
@@ -0,0 +1,35 @@
+package com.baeldung.security.manager;
+
+import org.junit.Test;
+
+import java.net.URL;
+import java.security.AccessControlException;
+import java.util.concurrent.Callable;
+
+public class SecurityManagerUnitTest {
+
+    @Test(expected = AccessControlException.class)
+    public void whenSecurityManagerIsActive_thenNetworkIsNotAccessibleByDefault() throws Exception {
+        doTest(() -> {
+            new URL("http://www.google.com").openConnection().connect();
+            return null;
+        });
+    }
+
+    @Test(expected = AccessControlException.class)
+    public void whenUnauthorizedClassTriesToAccessProtectedOperation_thenAnExceptionIsThrown() throws Exception {
+        doTest(() -> {
+            new Service().operation();
+            return null;
+        });
+    }
+
+    private void doTest(Callable<Void> action) throws Exception {
+        System.setSecurityManager(new SecurityManager());
+        try {
+            action.call();
+        } finally {
+            System.setSecurityManager(null);
+        }
+    }
+}
diff --git a/core-java-modules/pom.xml b/core-java-modules/pom.xml
index ecf1f4147e..082ffbef53 100644
--- a/core-java-modules/pom.xml
+++ b/core-java-modules/pom.xml
@@ -19,6 +19,7 @@
         <module>core-java-optional</module>
         <module>core-java-lang-operators</module>
         <module>core-java-networking-2</module>
+        <module>core-java-security-manager</module>
     </modules>
     
 </project>
diff --git a/java-blockchain/src/main/java/com/baeldung/blockchain/Block.java b/java-blockchain/src/main/java/com/baeldung/blockchain/Block.java
index 264e3c4b69..6b4e971cd7 100644
--- a/java-blockchain/src/main/java/com/baeldung/blockchain/Block.java
+++ b/java-blockchain/src/main/java/com/baeldung/blockchain/Block.java
@@ -3,7 +3,6 @@ package com.baeldung.blockchain;
 import java.io.UnsupportedEncodingException;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
-import java.util.Date;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -17,10 +16,10 @@ public class Block {
     private long timeStamp;
     private int nonce;
 
-    public Block(String data, String previousHash) {
+    public Block(String data, String previousHash, long timeStamp) {
         this.data = data;
         this.previousHash = previousHash;
-        this.timeStamp = new Date().getTime();
+        this.timeStamp = timeStamp;
         this.hash = calculateBlockHash();
     }
 
diff --git a/java-blockchain/src/test/java/com/baeldung/blockchain/BlockchainUnitTest.java b/java-blockchain/src/test/java/com/baeldung/blockchain/BlockchainUnitTest.java
index acbf651e78..883e55c351 100644
--- a/java-blockchain/src/test/java/com/baeldung/blockchain/BlockchainUnitTest.java
+++ b/java-blockchain/src/test/java/com/baeldung/blockchain/BlockchainUnitTest.java
@@ -3,6 +3,7 @@ package com.baeldung.blockchain;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.ArrayList;
+import java.util.Date;
 import java.util.List;
 
 import org.junit.AfterClass;
@@ -17,10 +18,10 @@ public class BlockchainUnitTest {
 
     @BeforeClass
     public static void setUp() {
-        Block genesisBlock = new Block("The is the Genesis Block.", "0");
+        Block genesisBlock = new Block("The is the Genesis Block.", "0", new Date().getTime());
         genesisBlock.mineBlock(prefix);
         blockchain.add(genesisBlock);
-        Block firstBlock = new Block("The is the First Block.", genesisBlock.getHash());
+        Block firstBlock = new Block("The is the First Block.", genesisBlock.getHash(), new Date().getTime());
         firstBlock.mineBlock(prefix);
         blockchain.add(firstBlock);
     }
@@ -28,7 +29,7 @@ public class BlockchainUnitTest {
     @Test
     public void givenBlockchain_whenNewBlockAdded_thenSuccess() {
         Block newBlock = new Block("The is a New Block.", blockchain.get(blockchain.size() - 1)
-            .getHash());
+            .getHash(), new Date().getTime());
         newBlock.mineBlock(prefix);
         assertTrue(newBlock.getHash()
             .substring(0, prefix)
diff --git a/pom.xml b/pom.xml
index 005a24effa..81338b9f81 100644
--- a/pom.xml
+++ b/pom.xml
@@ -579,7 +579,7 @@
 				
 				<module>spring-boot-nashorn</module>
 				<module>java-blockchain</module>
-				<!-- <module>Twitter4J</module> --> <!-- Builds locally, but fails in Jenkins, Failed to parse POMs -->
+			
 			</modules>
 
 		</profile>