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Linux Privilege Escalation : Exploiting SetUID Bit

Hello, aspiring Ethical Hackers. In this article, you will learn how to perform linux privilege escalation by exploiting SetUID. In our previous article, we have exploited cron jobs to change SetUID bit of an executable. What exactly is a SetUID bit?

SETUID stands for Set User ID on execution. This allows a user with low privileges to run a command with higher privileges. The difference between SUDO and SETUID is that in SUDO you can execute a command only if the root user can do it.

With the concept of SETUID understood, let’s see how binaries with SETUID bit set can be found. One way to find them is by using find command as shown below.

Here are some examples of gaining root privileges by exploiting programs with SETUID bit set.

1. bash

2. csh

3. env

4. nice

5. node

6. setarch

7. stdbuf

8. strace

9. taskset

10. tclsh

11. time

12. timeout

13. unshared

14. xargs

15. php

16. expect

17. find

18. python

19. flock

20. gdb

21. ionice

22. logsave

23. make

These are some examples of linux privilege escalation by exploiting SETUID bit.

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How Anti Malware works – identifies malware

Hello aspiring ethical hackers. In this article, you will learn how Anti Malware works. In our July 2020 Issue of Hackercool Magazine, our readers have seen one scenario where a malicious payload we created bypassed one of the Antivirus and successfully got a meterpreter session on the OMEGA target.

In this article, our readers will learn about more about Antivirus and Anti malware and how they work to detect malware. It is very important to understand how Anti Malware works in order to devise methods to bypass them in penetration testing. Anti Malware is a software just like malware. Different Anti malware use different methods to detect malware. Lets see each one of them.

Signature Based Detection

This type of Antivirus detects malware by comparing its code with known malware samples. This samples the Anti Malware uses for comparison are known as signatures. These signatures are regularly updated (in most cases, daily) by the anti malware in order to stay one step ahead of malware. This is the reason why antimalware needs regular updates.

Heuristic Detection

The problem with signature based detection is that it can only detect known malware or malware that is around more. To overcome this problem, many of the antivirus nowadays detect malware using heuristic analysis. In this type of analysis, the Antivirus tries to identify malware by examining the code in a virus and analyzing the structure of malware.
By doing this, the antivirus actually tries to simulate running the code and see what it actually does. If it finds any malicious intention in the code like the malware replicating itself or trying to rewrite itself, it classifies the code program as malware. As already mentioned, this is used by almost all modern antivirus or antimalware.

Behavioral Detection

In behavioral detection, the antivirus detects suspicious activity in the operating system. If the antivirus notices that any new program is trying to modify or make changes to system like altering files or running a code to communicate with external systems, then it flags the program as virus and blocks it. So instead of scanning the code of -the malware, it just scans for any suspicious activity.

Sandbox Detection

In Sandbox detection, the Antivirus classifies a program as malware after executing the program in a contained environment separated from the operating system. This contained environment is known as sandbox. If the program performs any suspicious or malicious activity in the sandbox, the antivirus classifies the program as malware. This method of detection takes a heavy toll on the system resources.

These are the ways in which antivirus can detect malware or payloads we create in penetration testing. There are a few other concepts you need to understand about antivirus.

Real Time Protection

Nowadays most antivirus use not just one but a combination of the above mentioned methods. Also, many antivirus nowadays are in Real Time Protection mode, i.e providing protection and on screen scanning of the system. In this, the antivirus detects and blocks the malware as soon as it enters the system. This is because it is more easier to detect malware as soon as it enters than after it has already infected the system.

False Positive

When an antivirus classifies a genuine program as malware, it is known as false positive. When this happens, the antivirus may classify genuine programs as malware and either remove them or block them, thus affecting operations.

False Negative

When an antivirus fails to detect malware or a malicious file as what it is or classifies it as a harmless file, it is known as false negative. False negatives pose a bigger dangerous problem because malware has gone undetected and stays on the system.
In PART 1 of our Bypassing Antivirus, our readers have seen the OMEGA target system failed to detect our batch payload. This is a case of FALSE NEGATIVE.

As already stressed in the PART 1 of this feature, the battle between malware and anti malware is ever evolving. There is no perfect anti virus that can detect 100% malware an d there are always false negatives that help hackers beat antivirus. This payloads which go undetected by antivirus are known as Frequently UnDetected (FUD) payloads. The best example of a FUD payload is Stuxnet.

That’s all fellows. I hope you got a basic understanding as to how anti malware works . In our future Issues of Hackercool Magazine you will learn more advanced methods used by black hats to bypass anti malware.

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Linux Privilege Escalation : Cron Jobs

Hello aspiring Ethical hackers. In this article you will learn how to exploit Cron jobs for Linux Privilege Escalation. If you are familiar with Windows Task Scheduler you will readily understand what cron is. Yes, it is used to schedule jobs or commands in Linux.
For example you have a Linux server and want to clean cache regularly once a day. You can do this manually everyday or schedule a job to do this daily without your intervention. Here’s where cron jobs assist you. You can assign a job in cron. Sometimes these jobs are assigned with root privileges and these can be exploited to gain root privileges. Let’s see it practically.

For this article, we have a target on which we already gained a shell. Then I ran the privilege escalation script on the target to find ways to elevate privileges on the target.

As I scroll down the output of our file, we can see our target has some cron jobs set.

As you can see in the above images, we can set cron jobs monthly, daily or hourly. But our job here is to not schedule cron jobs. It is to exploit them. As we scroll down further, we can see the format of a cron job.

In the above image, you can see the exact format of a cron job. It is minutes first, hours, day of month, month and day of week. We can see a cron job named /opt/ that is scheduled to run at the 00:00 time of first day of the first month of every year. That is the occasion of New Year.

But what does * * * * * mean? It means these cron jobs are scheduled to run every minute of every hour of every day of the week (i.e daily) , every month. That typically means these jobs run each and every minute. The important thing to notice here is that all these jobs are running as user “root”.

Let’s manipulate one the these scripts, let’s say /opt/ We have a SETUID bit set on “dash” shell, one of the shells installed on the target system.(We will see in a short while what SETUID is). This can be seen in the image below.

We are editing the file with a command “chmod u-s /bin/dash”. This will remove the SETUID bit. Wait for one minute and check the /bin/dash command.

The SETUID bit is removed. Not just that, we can add new users on the target system as shown below.

That’s how cron jobs can be exploited for linux privilege escalation.

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Bypass Antivirus with AV | ATOR

Hello aspiring Ethical Hackers. In this article you will see how to bypass Antivirus with AV | ATOR. AV | Ator is a backdoor generator utility that uses cryptographic and injection techniques to bypass AV detection. The AV in AV | Ator stands for Anti Virus. Ator is character from the Italian Film Series “Ator” who is a swordsman, alchemist, scientist, magician, scholar and engineer with the ability to sometimes produce objects out of thin air.

ATOR takes C# shellcode as input, encrypts it with AES encryption and generates an executable file. ATOR uses various methods to bypass Anti Virus. Some of them are,

Portable executable injection : In portable executable injection, malicious code is written directly into a process (without a file on disk). Then, this code is executed by either invoking additional code or by creating a remote thread. The displacement of the injected code introduces the additional requirement for functionality to remap memory references.

Reflective DLL Injection : DLL injection is a technique used for running code within the address space of another process by forcing it to load a dynamic-link library. This will overcome the address relocation issue.

Thread Execution Hijacking : Thread execution hijacking is a process in which malicious code is injected into a thread of a process.

ATOR also has RTLO option that spoofs an executable file to look like having an “innocent” extension like ‘pdf’, ‘txt’ etc. E.g. the file “testcod.exe” will be interpreted as “tesexe.doc” and of course we can set a custom icon. ATOR can be run on both Windows and Linux. We need Mono to run ATOR on Linux.

Let’s see how to install ATOR in Kali Linux. Clone the ATOR repository from Github as shown below.

Then unzip the zip archive.

Then, Install Mono as shown below.

After moving into the extracted directory, there will be an AVIATOR executable. We just need to run it with Mono.

If you want to run ATOR in Windows, you can just download the compiled binaries from Github . When you run the executable, the ATOR GUI opens.

Let’s see all the options in detail.
1. It contains the encryption key that is used to encrypt the shellcode. Keep it default if you want.
2. It contains the IV used for AES encryption. Keep it default too.
3. Shellcode in C# format.
4. It will show the encrypted payload.
5. The location to which the generated executable is to be saved.
6. Various Injection techniques.
7. Set a Custom Icon to the executable.

Let’s create the shellcode using msfvenom.

Copy the shellcode generated above and paste it in the payload column. Click on “Encrypt” to see the encrypted payload in (4). Click on (7) to set a custom icon (we are using pdf icon). Select the path of the executable (5) and select the injection technique (6) and click on “Generate EXE” button. Here’s the payload.

Before executing it on the target, start a listener on the attacker machine.

As soon the payload is executed on the target, we will have a shell as shown below.

See how to bypass antivirus with

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Cracking Wifi passwords automatically with Wifite

Hello aspiring ethical hackers. In this article, you will learn about a tool named Wifite. It is an automatic Wireless password cracking tool that tries almost all known methods of wireless cracking like Pixie-Dust attack, Brute-Force PIN attack, NULL PIN attack, WPA Handshake Capture + offline crack, The PMKID Hash Capture + offline crack and various WEP cracking attacks.
Wifite is installed by default on Kali Linux. Just like any wireless password cracking method, Wifite needs monitor mode to be enabled on the wireless interface as shown below. However, it automatically enables this monitor mode but if it fails to enable it, you can enable it manually as shown below.

Let’s see how Wifite works in cracking WEP, WPA and WPS enabled networks. Once everything is ready, open terminal and start Wifite using command as shown below.

It starts displaying all the wireless networks in your vicinity as shown below.

Let’s target the Access Point “Hack_Me_If_You_Can” which has WEP security enabled. Once you select the access point you want to target, hit CTRl + C and enter the number of that access point. In our case it is “1”.

As soon as you enter the number of that access point, Wifite tries out various attacks against the access point and grabs its password as shown below.

WEP is too easy. Let’s see how it fares in cracking WPA password. We start Wifite as shown above. Our target is once again “Hack_Me_If_You_Can”. However, as you can see it is secured with WPA now.

It starts attacking employing  various methods as shown below.

Now, let’s target a Access Point with WPS pin enabled.

As you can see, Wifite is successful in cracking WEP, WPA and WPS keys automatically without running any complex commands . Learn how to crack Wifi passwords with Besside-ng.