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Beginners guide to DoS attack

Hello, aspiring ethical hackers. In this blogpost you will learn about DoS attack. In April 2007, the government services, financial institutions and various media outlets of Estonia, a nation in eastern Europe were hit with a massive Denial of service attacks. The attack that almost crippled Estonia (almost all services of Estonia are based only online) coincided with the relocation of “Bronze soldier of Tallinn” a world war II monument which Russia objected to.

What is DoS attack?

DoS or Denial-of-Service attack is an attack that makes a website, service, network or software inaccessible to legitimate users. For example, imagine you are a user of Gmail. When you are trying to access Gmail to check an important mail sent from your office, you are unable to reach the servers of Gmail as there is a DoS attack on Gmail servers.

Types of DoS attacks

DoS attacks can be classified into three types. They are Volumetric attacks, Protocol attacks and Application layer attacks.

Volumetric attacks

In volumetric attacks, the bandwidth of the target network or service is exhausted, thus denying any legitimate users access to bandwidth. The magnitude of the attack is measured in bits-per-second (bps). Examples of these types of attacks are Ping of Death attack, UDP Flood attack, ICMP flood attack and Smurf attack.

1. Ping Of Death attack:

According to RFC791 IP, the maximum size of the packet should not exceed 65,535 bytes. In the Ping of Death attack, an attacker sends an oversized packet of size more than the prescribed limit with a ping request. (For example, a packet of size 65,550 bytes). The target system may crash while trying to reassemble this packet.

2. UDP Flood attack:

In this type of attack, an attacker sends a number of spoofed UDP packets to random ports of the target system. Target server tries to check for these applications (some of which are nonexistent) repeatedly. This causes exhaustion of the bandwidth in use thus replying to legitimate connections with a ICMP destination unreachable message.

3. ICMP Flood attack:

In the ICMP flood attack, the attacker sends a large volume of ICMP request (ping) messages to the target server either from a single IP or multiple IP addresses. The target server is bound to reply to these packets with a ICMP echo reply message thus exhausting the bandwidth.

4. Smurf attack:

In a smurf attack, the attacker sends ICMP echo request message to the broadcast network address spoofing the IP address of the target server. This makes all the devices in the network to reply to this echo request message with a echo reply message. Since the address of the target server is used in the echo request message, all the devices reply with this IP thus, making the target server inaccessible to the legitimate users.

Protocol attacks

In this type of DoS attacks, instead of exhausting the bandwidth, attackers try to exhaust resources available on the target network or website thus making it inaccessible to the legitimate users. Examples of these DoS attacks are SYN Flood attack, ACK Flood attack, TCP connection flood attack, Fragmentation attack and RST attack. This DoS attack is measured in Packets-per-second (pps).

1. SYN Flood attack:

In our blogpost on port scanning techniques, you learnt about the 3-way handshake.

In this attack, attackers exploit this 3-way handshake. How? The attacker sends multiple TCP SYN requests to the target server. When the target server responds to these SYN requests with a SYN/ACK packet, the attacker never sends a ACK message in response. This creates a partially open connection. By default, the target server or machines should track a partially opened connection for 75 seconds.

This is known as SYN flood. In these 75 seconds, the attacker can send large volume of SYN requests thus overloading the target system which eventually makes it inaccessible to the legitimate users.

2. Fragmentation attack:

Network or IP layer of OSI model allows packet fragmentation in order to overcome the problem of any higher-level protocol creating a packet larger than the size any particular local network supports. Attackers exploit this feature to send a large number (1500+bytes) of fragmented packets to the target server. The size of each fragment is usually reduced and small packet rate is used. This forces the target server to utilize a large number of resources to reassemble these fragmented packets thus causing DoS attack.

Application Layer attacks

In this type of DoS attacks, attackers exploit any vulnerabilities in the target server to prevent its access to the legitimate users. These vulnerabilities include cross site scripting, CSRF, File upload but most probably a Buffer overflow vulnerability. The magnitude of this attack is measured in requests-per-second (rps). Examples of this attacks include HTTP flood attacks and Slowloris attack.

1. HTTP GET/POST attack:

Browsers connect to the web server using HTTP requests. These requests can be either HTTP GET or HTTP POST. In this type of attack, attackers exploit these requests to perform DoS attacks.

In a HTTP GET DoS attack, attackers use time delayed HTTP headers to exhaust resources of webserver whereas in HTTP POST DoS attack the attacker sends HTTP requests with complete headers and without a message body or an incomplete message body.

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Beginners guide to Social Engineering

Hello, aspiring ethical hackers. In this blogpost you will learn about Social Engineering. Social Engineering is one of the most important techniques in Black Hat Hacking. It is used by APTs and Threat Actors even now.

What is Social Engineering?

Social Engineering is the art in which a human is convinced to perform actions which he is not intended to or shouldn’t be performing under normal circumstances. Hackers use social engineering to grab credentials, gather any required information about the organization or to gain initial access etc. It exploits human emotions like intention to trust, curiosity and other emotions.

Types of Social Engineering

Social Engineering can be classified into three types. They are: Human based, Computer based and Mobile based.

social_engineering

Human based Social Engineering

In human based social engineering, hacker interacts with a human personally to perform the attack. There are many types of social engineering attacks. Some of them are,

1. Dumpster diving:

Dumpster diving is a technique in which a hacker searches the dump or dustbin to gather any information about the organization.

2. Impersonation:

In this attack, attacker impersonates as another user to gather important information about any organization or performing hacking attacks. Any information obtained in dumpster diving can be useful in this stage. Obviously, an attacker will impersonate as a legitimate user of the organization or a person of authority or anyone else who has a chance to enter a company physically or virtually.

In June 2023, hacking group tracked as “Pink Drainer” impersonated journalists in phishing attacks to gain access to 1932 Discord and Twitter accounts. They stole approximately $29,97,707 worth of cryptocurrency.

3. Piggybacking:

Piggybacking is used to gain access to the premises of a company or organization. In piggybacking, a genuine employee of an organization allows access to the attacker because he/she thinks that the attacker has genuine reason to be on the organization’s premises. It usually happens when the hacker impersonates as anyone who is allowed into company’s premises. For example, delivery boy, technician etc.

4. Tailgating:

In tailgating, which is another social engineering techniques to gain illegal access to the company’s premises, a hacker tries to gain access to the company’s premises by quickly following behind a legitimate or genuine user immediately after he/she gains access into company’s premises.

5. Eavesdropping:

Eaves dropping is secretly listening to the conversation of employees of the organization etc. This can happen anywhere but mostly happens at recreational spots.

6. Shoulder surfing:

Shoulder surfing is the technique in which an attacker spies on the legitimate users of the organization by staying behind them. Shoulder surfing is normally used to see the legitimate user is entering his credentials but it can also be used to gather any valuable information.

7. Vishing:

In vishing, also known as voice phishing, a hacker uses voice over a phone or a VOIP call to perform social engineering.
In July 2020, hackers used vishing to trick Twitter employees into revealing account credentials of 130 Twitter account including that of Barack Obama, Joe Biden and Kanye West. The share value of Twitter plummeted by 7% after this incident.

8. Pretexting:

In pretexting, attacker creates specific scenarios or events by which the user he is targeting reveals information he/she makes.

Computer based Social Engineering

When a computer is used in an engineering attack, it is known as computer based social engineering attack. There are two types of computer based social engineering attacks. They are,

1. Phishing:

In phishing, attackers create a fake website (impersonating a genuine website) and divert the target users to this fake website to grab their credentials or make them download malware. There are multiple examples of hackers creating a fake phishing website to steal credentials, credit card information or other sensitive information. In August 2023, Supreme Court (the highest court of India) warned users about a fake website impersonating website of the Supreme Court trying to solicit personal details and confidential information from users.

2. Spear Phishing:

In spear phishing, a hacker selects specific users as targets and sends them an email with malware attached to the email and luring them to download and execute the attached payloads or take some other action. In February 2022, Russian hacking group known as Gamaredon, targeted Ukrainian government agencies and NGO’s with a spear phishing email campaign with malware laden emails.

Mobile based Social Engineering

If an engineering attack uses mobile it is known as mobile based social engineering. SMishing is a type of mobile based social engineering attack.

1. SMishing:

SMishing or SMS phishing is a phishing attack which is performed by sending a SMS to the target user’s mobile phone with a link to the fake website attacker created. In 2020, cyber criminals sent SMS messages to various user’s mobile phones asking them to click on a link to view important information about an upcoming delivery from United States Post Office (USPS). When users clicked on the links in these SMS, it took them to a malicious website that was designed to steal user’s Google account credentials.

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Password sniffing tutorial for beginners

Hello, aspiring Ethical hackers. In this article, you will learn about password sniffing. You should have observed that almost all the websites you have visited recently have a padlock sign and begin with HTTPS now. Google started giving minor ranking boost to websites with HTTPS enabled since year 2014. As you will learn by the end of the blogpost, there is a good security reason behind this.

What is Password sniffing?

Password sniffing or Credential sniffing is sniffing or capturing of credentials (or any other data) while they are in transit from one machine to another machine (usually from client to server). Password sniffing is only possible when plain text protocols are in use. Plain text protocols are those protocols in which confidential information like usernames and passwords are passed to the server in complete plain text and without any encryption.

This allows anyone in middle to sniff on these usernames and passwords. Examples of plain text or clear text protocols are FTP, Telnet, SMTP, HTTP, IMAP, POP3, TFTP etc. Let’s see password sniffing practically. In this article, we will demonstrate the basic level of password sniffing on plaintext protocols. For this, we will be using three virtual machines which are on the same network.

They are Metasploitable 2 which acts as server, Ubuntu which acts as client and of course Kali as our Attacker system. As you can see, the IP addresses of the three machines are

Metasploitable2 – 192.168.64.128 (Server)

Ubuntu – 192.168.64.132 (Client)

Kali – 192.168.64.132 (Attacker system)

Let’s start Wireshark on the attacker machine (on interface eth0). It starts capturing packets on the network.

The reason why we are using Metasploitable 2 as our target is that it already has many services that we need for this tutorial preinstalled. The first service we will be using is Telnet. It is a protocol that is used for remote access on another system. On most Linux systems, Telnet clients are installed by default.

So we open a terminal and log into the Metasploitable 2 Telnet server with the credentials shown below.

The login is successful. Now on the Attacker system, we can observe the traffic being captured by the Wireshark sniffer. You can see data related to Telnet being transferred.

We can Right Click on that Telnet data stream and click on “Follow” as shown below.

In the sub menu that opens when we click on the only option “TCP stream” a new window opens that will show only the TCP stream.

In this window, you can see the credentials we just used to login into the target system. Telnet is a plain text protocol which transfers credentials and other sensitive data in plain text. This allows sniffing of data. That’s the reason it has been mostly replaced by Secure Shell (SSH) nowadays.

Let’s see another protocol. File Transfer Protocol (FTP) is a protocol that is used to share files. It is another protocol that transfers data in plain text. From our client, we login into the FTP server with credentials “anonymous:anonymous”.

Anonymous account in FTP is used to share files to anyone without the need for them to know credentials.

On the Wireshark interface, you can see FTP data being transferred.

We can view the TCP stream

This once again shows credentials.

Instead of observing LIVE data transfer and following TCP stream from there, we can also just save the packet capture file and open the file later for analysis.

After opening the file, we can search for specific terms as shown below.

packet sniffing

Then following the TCP stream gives us the credentials.

Seeing the vulnerability due to sniffing, many protocols have been replaced with secure protocols which transfer data in encrypted form instead of plain text form. These are given below.

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Beginners guide to Steganography

Hello aspiring Ethical Hackers. In this blogpost, you will learn about steganography. Before you learn what is it, you need to learn why are we learning about it. In Feb 2023, Red Eyes Hacking Group (APT37) used a jpg image as attachment in one of their spear phishing email. When victims clicked on this image, it triggered an exploit that ran shellcode on the victim’s computer to download and execute a malicious payload that is stored within the jpg file mentioned above. But how was the malicious payload was hidden inside the jpg image?

What is Steganography?

It is an art or technique of hiding secret or any precious information inside something that looks common & ordinary. This information is hidden in such a manner that its presence is not evident to the human inspection. The word stegano graphy came from Greek word steganographic, that is combination of words steganos (meaning hidden or concealed) and graphia (writing).

In ancient and medieval times, kings used steganography to forward messages secretly. Greeks were the fist to use it. Coming to modern times, hackers are using it to hide malicious code in images, text, files, audio, video film and any other medium that looks benign.

Types of Steganography

There are five types of stegano graphy. They are,

  1. Text stegano graphy
  2. Image stegano graphy
  3. Video stegano graphy
  4. Audio stegano graphy
  5. Network Stegano graphy
steganography

1. Text Steganography::

In text steganography, the secret information is hidden in a piece of text. For example, let’s say a text contains “Indians love Unity”. This may look like an ordinary or normal text. But just take the first letter of these three words. That becomes “ILU” a shortcut for I Love You message used by youngsters.

2. Image Stegano graphy:

As you might have already expected, when the secret information is hidden in an image (digital image) it is known as Image steganography.

3. Audio Steganography:

If the information we want to hide is hidden in an audio, it is known as audio steganography. Humans can hear sound that only contains certain frequencies. So, by altering the properties of audio like frequency, amplitude etc. secret messages can be hidden. However, to be able to receive and understand this secret information, the receiver needs to have smart listening devices to decipher the hidden information.

4. Video Steganography:

If the secret information is hidden in a video, it is called video steganography. A video is simply a representation of a sequence of consecutive images. So, we can say that this is an advanced version of Image steganography.

5. Network Steganography:

Considered to be more advanced and practically useful to Black Hat Hackers, in Network steganography information is hidden in network traffic. For example, it can be hidden in the TCP/IP headers etc.

Examples of Steganography attacks in hacking

  1. In September 2022, researchers at ESET discovered a previously unknown Threat actor they named Worok hiding malicious payload in PNG files.
  2. In 2019, researchers at Symantec observed a Russian cybersecurity group waterbug (also known as just the malicious) delivering a publicly known backdoor by hiding it in a WAV file.
  3. In the same year, security researchers at Cylance observed a hacking campaign that was delivering XMRIG Monero CPU miner by hiding them in WAV files.
  4. PLATINUM hacker group, that usually targets Governments of South Asia and South East Asia, embedded their malware commands in the HTML code of a website. They achieved this by encoding malware commands in a specific sequence of “TAB” and “SPACE” bar.

In future steganography is going to increase in cyber security.

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Privilege Escalation guide for beginners

Hello aspiring Ethical Hackers. In this blogpost, you will learn in detail and clearly about Privilege escalation. Privilege escalation is an act of gaining elevated access to resources that are normally restricted to an application or user. To understand privilege escalation better, you need to first understand about privileges. Since hacking mostly deals with exploiting of operating systems, let me explain you about how privileges in a operating system are assigned.

Since Operating Systems (OS) are meant for user interaction and perform some specific functions you should have noticed that different users are assigned different privileges on a system.

Let’s see the example of the Windows operating system. Windows OS has generally 7 types of accounts. When I am talking about accounts, I am talking about local user accounts instead of remote or online accounts. A local user account is defined locally on a device (computer) and are assigned rights and permissions on that particular device only. The types of Windows user accounts are given below.

When you do a fresh installation of Windows (Windows 7 to 11), the first user account that is created during setup is the Administrator account, As the name suggests, the Administrator account is a default local user account (account created during Windows installation) used for system administration. This account has full control of the files, directories, services and other resources on the local device. As you might have experienced by now, an administrator account can create, delete and assign permissions to other users.

This default Administrator account can neither be deleted or locked but it can be disabled or renamed. Windows setup disables the built-in administrator account after installation of Windows and creates another local account that is a member of the administrators group.

The newly created user belonging to the Administrator group has same powers as the default administrator account. Since this is too risky if some malicious user gains access to the system as Administrator user, Windows provides option to create an account called standard account. Most organization provide their workers a standard account. A standard account on Windows can run almost all application on a Windows system and perform all other day-to-day computing tasks.

However, to perform some tasks like installing programs or applications, making changes to the registry etc and other operations that require elevated privileges, the standard user is asked for credentials of Administrator of the system through the user Account control. Simply put, you cannot make any major changes to the operating system with standard account.

Apart from these two accounts, Windows has some default local user accounts that are automatically created while operating system is installed. They first one you need to learn about is the “SYSTEM” account. This account is used by the operating system and its services running under Windows. This account doesn’t show up in user manager which means you cannot login with this account.

It belongs to Windows and used by all Windows processes. You can view the processes running with this “SYSTEM” privileges from details tab of the Window Task Manager.

The ms08_067 vulnerability affected a process svchost.exe that runs with SYSTEM privileges. So, once you exploit it, you automatically get SYSTEM privileges. It can be exploited remotely and grant SYSTEM PRIVILEGS to attackers. No wonder it is considered very CRITICAL.

Another local default user account is the “Network service” account. This account is used by the service control manager (SCM). It is used to present the computer credentials while it is communicating with remote servers. Similarly, Windows has an account called “Local Service” which is also used by the service control manager. It has minimum privileges on the local computer.

Linux systems too have different types of user accounts. They are 1) Super user account 2) Regular account 3) System account 4) Service accounts.

On Linux, the Super User account is the most powerful account and is the default administrator of the Linux system. This account is popularly known as root account. The root account has unlimited control on the Linux system and you can literally do anything you want with this account.

The root user in Linux has (#) symbol on their terminal. All other users who are later added are together known as regular accounts. Regular accounts are similar to “standard account” on Windows and to perform administrative actions on the OS, they need to use sudo or su command. Apart from these two accounts, Linux has “system account” and “service account” that are created during the installation of the OS and are by OS processes just like “SYSTEM account on Windows. However, these accounts don’t run with superuser privileges. Service accounts are created whenever a service is installed on the system.

Since you are now accustomed with privileges and user accounts with different privileges, you can now understand privilege escalation.

What is privilege escalation?

Privilege escalation is an act or process of gaining access to privileges of the other user account using any means or techniques. Normally privileges of user account with higher privileges are targeted by hackers.

Privilege escalation is of two types: They are,

  1. Horizontal privilege escalation.
  2. Vertical privilege escalation.

1. Horizontal Privilege Escalation:

In horizontal privilege escalation, an attacker gaining access to the privileges of another user with same rights as him but with access to some other resources. For example, imagine on a Linux system, you gained access as a regular user (user_1). On the same system, there is another regular user (user_2) with same rights as him but with access to the MySQL databases. Elevating privileges to this user (user_2) can give you access to MySQL database.

2. Vertical Privilege escalation:

In cyber security or hacking, when anyone says “privilege escalation”, they are talking about this type of privilege escalation most of the time. In vertical privilege escalation, an attacker with low privileges tries to gain access to higher privileges.

Techniques used for Privilege escalation

Attackers use various techniques to elevate privileges. Some of the most general techniques are given below.

1. Social Engineering:

In Social Engineering, attackers somehow convince high privileges users to give access their credentials. These techniques include phishing, spear phishing attacks etc. For example, let’s say the attackers gained access to the email of the user with low privileges. From this email, he/she can send an email to the user with high privileges and somehow convince him/her to give any credentials.

In the first week top of September 2023, Okta, a company providing Identity services warned its users of social engineering attacks to obtain super administrator privileges on the organizations using Okta’s services. In these attacks, attackers performed social engineering attacks against IT service desk personnel by calling them and convincing them to reset multi-factor authentication (MFA’s) of high privileged users. Then attackers (allegedly APT Muddled Libra) abused these high privileged super admin accounts to impersonate users of the compromised organizations.

2. Password cracking:

Sometimes attackers crack the passwords of high privileged users to be used in privilege escalation.

3. Exploiting vulnerabilities:

This is one of the popular methods of escalating privileges. In this technique, attackers exploit vulnerability in software installed on the target system to elevate privileges. For example, PrintNightmare, Zerologon, Fodhelper etc in Windows and Dirtypipe, DirtyCow, PWNKIT, Netfilter, Heartbleed and Looney Tunables.

4. Misconfigurations:

In this type of attack, attackers use any misconfiguration on the target system for privilege escalation. These misconfigurations can include weak passwords, setting empty string as password, unsecured network service, open ports and exposed services etc. Examples are exploiting cronjobs and exploiting SetUID bits etc.

Many APT’s and Threat Actors exploit the recently (before patches are applied) released local privilege escalation vulnerabilities to elevate their privileges.