Process won't show in the process list. Lets try putting this loop together first, but just print the d_name of each entry to the kernel buffer - then well worry about how to stop certain directories from being presented to the user. This might seem like a simple technique to pull off, but its only because were repurposing two different syscall hooks that weve already covered: sys_kill() in Part 3 and sys_getdents()/sys_getdents64() in Part 6. It would probably be a good thing to install and run rkhunter. We can see sys_getdents64 being called with all its arguments and that its written 600 bytes into the buffer we provided. See examples below. Furthermore, the process to hide can be selected after authenticating with the rootkit . This article introduces an unconventional method to hide Linux process from users, with only one line of code: Modify the pid of the process. For example, let's assume sshd is running on our system. . Simply build and run sandfly-processdecloak for your preferred Linux platform using the built in scripts. In the full rookit (on the repo), there are four hooks in total: one each for sys_getdents and sys_getdents64 as well as another two for the pt_regs and old-fashioned calling convention for each of those. The only gotcha is what to do when there is no previous entry, i.e. S 0:00 /usr/sbin/sshd 4721 tty1 S 0:00 grep sshd. Once we put together the rest of the kernel module (Ftrace, etc), we can build it and try it out. In their hopes to move away from 32-bit systems, the kernel developers removed the definition of linux_dirent (note the absense of 64) from the kernel headers. The hook for sys_kill() should look something like this (as always, Im only illutrating the hook that uses the more modern pt_regs method of calling - more info can be found in Part 2): Now that we can tell the rootkit which PID wed like to hide, we have to actually hide it! How to constrain regression coefficients to be proportional. We can find its definition in include/linux/dirent.h. https://github.com/dsmatter/brootus bROOTus is a Linux kernel rootkit that comes as a single LKM (Loadable Kernel Module) and it is totally restricted to kernel 2.6.32. https://github.com/jarun/keysniffer A Linux kernel module to grab keys pressed in the keyboard. Written in Golang and is portable across multiple architectures with no modifications. rev2022.11.4.43008. I check the content of buf. The secret boogaloo file gets hidden from the user! Thanks for contributing an answer to Server Fault! You can read about here: We do not have a copy of Drovorub to test detection yet, but we will be adding more capabilities to sandfly-processdecloak to decloak other LKM rootkit variants. I was thinking another approach, as in task_struct link list contains all the process names, if I can somehow unlink the target process from task_struct that should do the trick, but I do not have any idea how to do that. Like kernel rootkits, these can reduce the performance of your RAM memory, by occupying the resources with all the malicious processes involved. Again, only the new parts are commented: Its worth taking a bit to absorb whats going on here and it would be no bad thing to go back and re-read each of the three versions of the hook and their explanations - it certainly took me a long time to write them using several different sources! This time around we need be a little cleverer. Asking for help, clarification, or responding to other answers. Asking for help, clarification, or responding to other answers. Is my understanding is correct? To do this, well use memmove(), but we also have to remember to decrease ret by d_reclen too so that we dont run over the end of the buffer as we loop through the rest. How can I increase the full scale of an analog voltmeter and analog current meter or ammeter? In our case we will compare d_name to a predefined prefix string as way of deciding which entries to hide. To do this, we need yet another linux_dirent64 struct, which well call previous_dir, and update it as we loop through everything. Are Githyanki under Nondetection all the time? How do I simplify/combine these two methods for finding the smallest and largest int in an array? This is because nearly all userspace tools that give us information about processes just read the contents of the /proc/ filesystem. The Linux Rootkit, outlined in Malware: . A rootkit contains a set of tools and replacement executables for many of the operating system's critical components, used to hide evidence of the attacker's presence and to give the attacker backdoor access to the Linux Rootkits One way an intruder can maintain access to a compromised system is by installing a rootkit. Did Dick Cheney run a death squad that killed Benazir Bhutto? LKM rootkits often hide entries in /proc because processes not visible in /proc will not be visible with standard system tools like ps, netstat, and so on. Thanks for contributing an answer to Stack Overflow! -Recall the goal of rootkits is to hide things: processes, files, and network connections. Rootkits can modify system files to give the hacker access to sensitive information or disable security features. Use the following command to detect all binary files that can display processes: If it's . This is quite an old exploit (2011), and hasn't likely functioned for quite a while. The last thing we need to figure out is how to get the system to skip over any entries we find that start with our prefix boogaloo. How can I safely create a nested directory? Linux LKM Rootkit Tutorial | How To Protect Yourself From MALICIOUS LKM Rootkits | Part 3 - I show you two programs rkhunter, and chkrootkit that can help y. All you have to do is remount the /proc filesystem with the Linux kernel hardening hidepid option. The rough outline of our hook will look like this: Hopefully by this point, the above skeleton makes perfect sense. Possible kernel level rootkit. Features Hide process Hide process CPU usage Hide files that his filename starts with the MAGIC_PREFIX Rootkit installation Build $ git clone https://github.com/alfonmga/hiding-cryptominers-linux-rootkit $ cd hiding-cryptominers-linux-rootkit/ $ make Loading LKM: And thats pretty much all there is to it! To hide a process from the ps|| pstree etc. kandi ratings - Low support, No Bugs, No Vulnerabilities. Does activating the pump in a vacuum chamber produce movement of the air inside? Do any Trinitarian denominations teach from John 1 with, 'In the beginning was Jesus'? According . By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. User-mode rootkits are simpler and easier to detect than kernel or boot record rootkits. Connect and share knowledge within a single location that is structured and easy to search. Copy the binary onto your hosts you want to check and run it. One technique is to change the process name using: prctl (PR_SET_NAME, (unsigned long) "NewName", 0, 0, 0); ..and if possible to fork () and let the parent process die. It might be that OSSEC is using the unhide utility to check for hidden processes. Not only can Sandfly decloak hidden PIDs, but we also can detect cloaked data in files, cloaked directories and more. At this point, we realise that well have to allocate our own buffer into kernel space, modify it there and then copy it back (just like in Part 5). 1. It is impossible to hide the process unless one starts messing around in the kernel to limit this. Below is the annotated (and trimmed) output that I got: Okay, this is a bit clearer. Because we are an agentless product, we are able to get onto a large number of Linux hosts to investigate them for LKM rootkits without any system impacts or risks to system stability. In order to loop through these structs, we will introduce an offset variable, initially set to 0, and a current_dir variable defined as another linux_dirent64 struct. as for procfs, addtional check is needed, everthing under our hidden /proc/PID should be hidden too. Please report false positives to us if you find them. The first is the record length and is the total size of the struct in bytes. In particular, we see that its got two interesting fields; d_reclen and d_name. The brute technique consists of bruteforcing the all process IDs. Most rootkits/malware use the power of the kernel to hide, they are only visible from within the kernel. As usual, lets try to understand that underlying kernel functionality that we are hoping to influence before writing anything. . @mevets My kernel version is 5.3.0-45-generic. Very lightweight and will not hook into the kernel or cause system instability. The solution is to just define it yourself, as I did on line 116 of rootkit.c in the repo. How often are they spotted? It should be clear what the new parts are doing (look for the comments), but if not, try re-reading the paragraph above it. There is a slight caveat that we will hide all files or directories with the name of the PID were hiding. Trend Micro says that KORKERDS' authors modified the rootkit to hide the cryptominer's main process from Linux's native process monitoring tools. The trick that we are going to use is to increment the d_reclen field of the entry before the one we want to hide by the d_reclen value of the boogaloo entry. Therefore we need to come up with a way to tell our module which PID we want to hide. 6. Success! Making statements based on opinion; back them up with references or personal experience. Let's look in /proc/1431 to obtain more information about the . Our objective is to hide our reverse shell connection process on the target Linux system in order to avoid detection. Therefore, they are spread by the attacker by such tactics that the user is unable to notice that something is wrong with the system. To start us off, the function declaration is: This macro translates to the slightly more familar: That linux_dirent64 struct is what contains the information about the directory listings (dirent is short for directory entry). Memory rootkit. To make it harder to spot a cryptominer process that is utilizing all of the CPU, a new variant has been discovered for Linux that attempts to hide its presence by utilizing a rootkit. Skidmap Malware Uses Rootkit to Hide Mining Payload. It was reasonable to assume initially those executables were modified in some way to hide information, but this possibility was ruled out by comparing them with versions known to be . Is there a way to make trades similar/identical to a university endowment manager to copy them? Usually by hiding them in devious software that looks legitimate and could be functional. It only takes a minute to sign up. As in previous parts, Im only going to go through the pt_regs version of the syscall hook, and in this case, Ill only go through hooking sys_getdents64. 4 different ways of hiding a #Linux process Click to tweet Sysdig Let's see if sysdig can be tricked as well, starting by CPU usage: gianluca@sid:~$ sudo sysdig -c topprocs_cpu CPU% Process ------------------------------ 99.99% evil_script.py 2.46% sysdig 0.27% java 0.03% sshd And network activity: This process involved accessing the system over Telnet, and modifying/creating files ipv6.o, init and rpc.status. Making location easier for developers with new data primitives, Stop requiring only one assertion per unit test: Multiple assertions are fine, Mobile app infrastructure being decommissioned. Its only slightly different from where we started in Part 5, but in that case the only fiddling we did was overwrite the kernel buffer with 0x00 before copying it back to userspace. To remove a rootkit, it is often necessary to reinstall the operating system. Horror story: only people who smoke could see some monsters, Best way to get consistent results when baking a purposely underbaked mud cake. sandfly-processdecloak is a utility to quickly scan for Linux Process IDs (PIDs) that are hidden by common and not-so-common loadable kernel module stealth rootkits and decloak them so they are visible. to get a file descriptor (3), # Check the directory pointed to by file descriptor 3 exists, # Call getdents64 syscall with the file descriptor and a pointer to userspace, /* Pull the userspace dirent struct out of pt_regs */, /* Declare our kernel version of the buffer that we'll copy into */, /* Call the real getdents64, and allocate ourselves a kernel buffer */, /* Check that neither of the above failed */, /* Copy from the userspace buffer dirent, to our kernel buffer dirent_ker */, /* Copy dirent_ker back to userspace dirent */, /* Declare current_dir pointer and the offset variable */, * Note that we have to cast dirent_ker to (void *) so that we can add, /* Compare the first bytes of current_dir->d_name to PREFIX */, /* Increment offset by current_dir->d_reclen so that we iterate over, /* Declare the previous_dir struct for book-keeping */, /* Check for the special case when we need to hide the first entry */, /* Decrement ret and shift all the structs up in memory */, /* Hide the secret entry by incrementing d_reclen of previous_dir by, * that of the entry we want to hide - effectively "swallowing" it, /* Set previous_dir to current_dir before looping where current_dir, Privileged Container Escapes with Kernel Modules, Linux Rootkits Part 5: Hiding Kernel Modules from Userspace, Linux Rootkits Part 6: Hiding Directories. This makes it difficult to detect, as infected systems . This tool sometimes raises false-positives. This is useful because it lets us easily jump through these structs in memory looking for what we want. Why are statistics slower to build on clustered columnstore? Stack Exchange network consists of 182 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Permissive License, Build not available. Connect and share knowledge within a single location that is structured and easy to search. The best way to know whether your server has been "rooted" is to be running a host-based intrusion detection system (HIDS). Rear wheel with wheel nut very hard to unscrew, Non-anthropic, universal units of time for active SETI. The best answers are voted up and rise to the top, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company, How to view linux hidden process and remove rootkit, Making location easier for developers with new data primitives, Stop requiring only one assertion per unit test: Multiple assertions are fine, Mobile app infrastructure being decommissioned. What can I do if my pomade tin is 0.1 oz over the TSA limit? How to view hidden files using Linux `find` command. Is there a trick for softening butter quickly? All this is a bit much, so lets take a concrete look at what listing a directory actually looks like with strace ls. Excessive number of hidden processes. Transformer 220/380/440 V 24 V explanation, Replacing outdoor electrical box at end of conduit. A rootkit is a group of software tools used by an attacker to cover his or her tracks. This technique is only available on Linux 2.6 kernels. Terms & Privacy Policy. how to move packet from NF_INET_PRE_ROUTING to NF_INET_POST_ROUTING? You can check yourself by running I cannot find an authoritative statement on that. Are there small citation mistakes in published papers and how serious are they? It is less than used/RSS. The easiest way to do this is to just hook sys_kill() again because its already built to send a PID to the kernel! In this case, the file has other suspicious attributes such as being marked as immutable and also the rootkit was not allowing . Lets finish off this syscall hook. This is because nearly all userspace tools that give us information about processes just read the contents of the /proc/ filesystem. The proper time to install a HIDS is when the server is first installed, and before it is put onto a network. Linux rootkit to hide a PROCESS 328 views Oct 28, 2021 usm durr 197 subscribers 6 Dislike Share Linux rootkit to hide a process. Success! What is the difference between a process and a thread? Is my understanding is correct? How to list hidden file/process/regKeys by rootkit, Rootkit attack by inserting new binary formats. When the migration is complete, you will access your Teams at stackoverflowteams.com, and they will no longer appear in the left sidebar on stackoverflow.com. Were going to combine a few of these techniques now in order to hide certain files and directories from userspace. Hope you enjoyed working through this one - Well Done for making to the end! Its still in the kernel, but because its not in the headers, your module will fail to build. This is a rootkit i developed some time ago for educational purposes. Works against LKM rootkits such as Diamorphine, Reptile and variants. Rootkits can also contain software which allows the attacker to obtain root access and steal or remove files on a system. Steps: -. To learn more, see our tips on writing great answers. Now that we know how to hide directories (see last time), we can also hide processes! Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Which kernel version are you running? We can check this by looking at the output of strace -e openat ps or strace -e openat top. I've a working code that looks like original Kbeast code. To learn more, see our tips on writing great answers. You can use the ps tool to obtain sshd's Process ID (PID): [notroot]$ ps x | grep sshd 1431 ? User-mode or application rootkit. This malware is notable for how it loads malicious kernel modules to keep its cryptocurrency mining operations hidden. The big difference here is that we cant simply overwrite the entire buffer with 0x00, but instead we have to look at this buffer as the struct it really is and loop through its members. If you wanted to be extra sneaky, you might be able to find a way to prevent being able to read or write to a file, but still allow it to be executed? And so on we go, until offset is equal to the ret - the value returned by orig_getdents64. Processes that are trying to hide are revealed with their PID and process name they are currently using. Support for more than one PID is left for you to try. We will focus on the 64-bit version, sys_getdents64, for now. In this case, well need to shift everything up in memory by the d_reclen value of the first entry. This works by using a vulnerable program to obtain root privileges as a regular user, called privilege escalation. LKM rootkits often hide entries in /proc because processes not visible in /proc will not be visible with standard system tools like ps, netstat, and so on. This gives us two results, as mentioned earlier; one for 32-bit and another for 64-bit. Hope you enjoyed this one - its a little shorter than usual but thats only because there isnt much new here, just a clever combination of techniques weve already covered. This is because strlen(hide_pid) will be 0, so the call to memcmp() will always return true. and what maximum damage it can do. rev2022.11.4.43008. The only downside is that we can only hide one PID at a time. In total, youll have four copies of essentially the same hook. Does the Fog Cloud spell work in conjunction with the Blind Fighting fighting style the way I think it does? The only difference will be that we will write the PID passed to signal 64 into a global hide_pid variable, rather than just ignoring it. Skidmap, a Linux malware that we recently stumbled upon, demonstrates the increasing complexity of cryptocurrency-mining threats. Rootkits are collection of tools that are used to provide backdoor access for Trojan horses by modifying important system files. Then well set current_dir = dirent_ker + offset. The way we do that is by taking the hooks for sys_getdents() and sys_getdents64() from Part 6, and replacing the line that compares current_dir->d_name to the PREFIX with one that compares it to hide_pid - see line 72 of the new rootkit.c: Note that we also have to make sure that hide_pid isnt empty! To subscribe to this RSS feed, copy and paste this URL into your RSS reader. If the letter V occurs in a few native words, why isn't it included in the Irish Alphabet? We do further checks in critical system areas for files loading kernel modules but are hiding this data from view. The syscall reference directs us to fs/readdir.c, where we find the definition for sys_getdents64. How can i remove that. What did Lem find in his game-theoretical analysis of the writings of Marquis de Sade? Below we show the Reptile rootkit hiding the built-in backdoor reptile_shell, a test process called reptile_hidden and a socat program being run as another backdoor. Sandfly uses a variety of methods to detect and decloak LKM style rootkits in more extensive ways than this free tool does. Malware Rootkits Linux Security Linux Forensics. Only root can see all process and user only see their own process. command it has the following function. 6. To begin with, current_dir will just be the first struct in memory, and we can memcmp current_dir->d_name with our prefix (defined above as boogaloo). # Call execve syscall to execute "ls" with no arguments (and 72 environment vars), # Redacted: Loading various libraries like libc into memory, # Call openat syscall with directory "." Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. I think I saw 2.16; uname -r on my machine shows:4.15.0-74-generic. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Stack Overflow for Teams is moving to its own domain! Should we burninate the [variations] tag? Is God worried about Adam eating once or in an on-going pattern from the Tree of Life at Genesis 3:22? Would it be illegal for me to act as a Civillian Traffic Enforcer? Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. If you were to do that periodically it makes it harder to track down the . Find centralized, trusted content and collaborate around the technologies you use most. Our hooks will call the real syscalls as normal, and then we will repeat the technique from Part 5, making use of copy_from_user() and copy_to_user() to alter the buffer that is returned to userspace. Does it make sense to say that if someone was hired for an academic position, that means they were the "best"? Making statements based on opinion; back them up with references or personal experience. It a match found then, free the kernel buffer kbuf. Unfortunately, if you're not running a HIDS now, then it's too late to install one. The description of the project says "An LKM rootkit targeting Linux 2.6/3.x on x86(_64), and ARM". Stack Overflow for Teams is moving to its own domain! At Sandfly we hate false positives and do everything we can to reduce or eliminate them to not waste your time. sandfly-processdecloak will analyze the entire valid Linux PID space to check that each running PID in fact is visible as it should be. At this point, weve used several different techniques to manipulate the kernel into doing interesting things. The tool leverages a Process ID (PID) bruteforce tactic to find processes that are not showing themselves in the standard /proc directory listing on Linux. How to view linux hidden process and remove rootkit. Because we want to control what this syscall returns to the user, it is helpful to take look at what this syscall actually does. My understanding is *buf, contain the name of the process it is trying to hide. The Trojan from last year called Hand of Thief failed in its ambitions to be the first banking Trojan for Linux desktops. We have released a new tool called sandfly-processdecloak to help find and decloak Linux stealth rootkits automatically. It enables hiding processes, files, and even the kernel module, making it harder to detect. My understanding is *buf, contain the name of the process it is trying to hide. The /proc system stores a lot of system information, including process information. PIDs are very unpredictable, so we dont want to hardcode one into our rootkit. You can use unhide or tool such as rkhunter to scan for rootkits, backdoors, and possible local exploits. In what follows, only the new parts are commented. Another way to detect a rootkit is to look for changes to system files. How to run a server on port 80 as a normal user on Linux? Implement hiding-cryptominers-linux-rootkit with how-to, Q&A, fixes, code snippets. Memory rootkits hide in the RAM memory of your computer. It a match found then, free the kernel buffer kbuf. A computer system or a computer network can be infected with Trojan . Is it OK to check indirectly in a Bash if statement for exit codes if they are multiple? It is notable for being bundled with a rootkit component ( Rootkit.Linux.KORKERDS.AA) that hides the malicious process' presence from monitoring tools. If you want, you can try compiling this and check that it works (you might want to wait until the end, because youll have to copy it out four times!). We can leverage Rootkits on Linux systems to hide our processes from the process tree in order to avoid detection by system administrators or security analysts. Server Fault is a question and answer site for system and network administrators. I and just installed OSSEC and it is telling this. We begin by checking the Linux Syscall Reference for sys_getdents. Instead, rootkits actually depend on that attacker/malicious user already has already exploited the target and gained root . When the migration is complete, you will access your Teams at stackoverflowteams.com, and they will no longer appear in the left sidebar on stackoverflow.com. Its my live server and i host around 20 sites on it. * hide_pid will store the string representation of the PID we're hiding, * Declaration for the real sys_kill() function, * Pull out the arguments we need from the pt_regs struct, * If the signal is 64, then print a message to the kernel buffer and, * Otherwise, just return the real sys_kill, /* Hide the directory with name in hide_pid */, Privileged Container Escapes with Kernel Modules. Hiding Linux Processes With Libprocesshider. This is definitely the trickiest technique to get your head around due to how many steps it involves. This function override sys_call_table [__NR_write]. Note is small hidden, so, it is not worth countering, tease 1 senior meeting engineer to engage in a prank to play. Its worth pointing out that the file is still there and you can go ahead and open it, delete it, etc without any trouble, but dont expect it to show up in ls! Its possible to flag a legitimate PID that is not actually cloaked but weve taken measures to limit this risk. Its my live server and i host around 20 sites on it. We recently encountered a cryptocurrency-mining malware (detected by Trend Micro as Coinminer.Linux.KORKERDS.AB) affecting Linux systems. Linux Stealth Rootkit Process Decloaking Tool sandfly-processdecloak, 4 Ash Street Christchurch, New Zealand 8011. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Freeze and unfreeze processes transparently?
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