Here is the definition from fs/readdir.c if youre trying to work it out yourself without peeking at my version: Lets take a look at what happens when we go ahead and load this rootkit after creating a file that wed like to hide. In our case we will compare d_name to a predefined prefix string as way of deciding which entries to hide. Inspecting Malicious LD_PRELOAD Library. Another way to detect a rootkit is to look for changes to system files. 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. Its still in the kernel, but because its not in the headers, your module will fail to build. 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. The secret boogaloo file gets hidden from the user! To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Works against LKM rootkits such as Diamorphine, Reptile and variants. 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. Now the file of interest in the entire rootkit is /lib/libcurl.so.2.17..This file being referenced in /etc/ld.so.preload means that it is the one that is intercepting system calls to do the grunt work of the rootkit to hide. Malware Rootkits Linux Security Linux Forensics. 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. upon running the ps command, it shows the following. The likelihood of this being spotted is pretty low. It is less than used/RSS. It is notable for being bundled with a rootkit component ( Rootkit.Linux.KORKERDS.AA) that hides the malicious process' presence from monitoring tools. 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. 6. Asking for help, clarification, or responding to other answers. 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: Memory rootkit. using copy_from_user(), buf is copied into a kernel buffer kbuf and then upon detecting the ps||pstree|| command using strstr(), it looks for the process_to_hide(H4X0R). If you see it only once, it could be that there was a delay between when OSSEC got the info from ps (say) and then it checked it against /proc. command it has the following function. Making statements based on opinion; back them up with references or personal experience. 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. The best way to know whether your server has been "rooted" is to be running a host-based intrusion detection system (HIDS). 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). This is definitely the trickiest technique to get your head around due to how many steps it involves. Please report false positives to us if you find them. Does activating the pump in a vacuum chamber produce movement of the air inside? 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. Are there small citation mistakes in published papers and how serious are they? Is there a trick for softening butter quickly? LINUX To hide a process, remove the process from the list of prev_task and next_task Leave next_run and prev_run alone. "The rootkit hooks the readdir and readdir64 . Let's look in /proc/1431 to obtain more information about the . Hiding Linux Processes With Libprocesshider. # 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 "." 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 . 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! A rootkit is a group of software tools used by an attacker to cover his or her tracks. The brute technique consists of bruteforcing the all process IDs. Yes, it is a little bit old, but I thought tweaks it a little bit might work with the current version. This gives us two results, as mentioned earlier; one for 32-bit and another for 64-bit. 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. You can use unhide or tool such as rkhunter to scan for rootkits, backdoors, and possible local exploits. To remove a rootkit, it is often necessary to reinstall the operating system. 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. I think I saw 2.16; uname -r on my machine shows:4.15.0-74-generic. I've a working code that looks like original Kbeast code. Excessive number of hidden processes. when opening pathname with SECRET suffix, we drop the suffix and use orig_openat to open the target file. It is impossible to hide the process unless one starts messing around in the kernel to limit this. How to view hidden files using Linux `find` command. My understanding is *buf, contain the name of the process it is trying to hide. Processes that are trying to hide are revealed with their PID and process name they are currently using. Stack Overflow for Teams is moving to its own domain! Connect and share knowledge within a single location that is structured and easy to search. Does the Fog Cloud spell work in conjunction with the Blind Fighting fighting style the way I think it does? Rootkits; Scenario. Stack Overflow for Teams is moving to its own domain! 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). 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. In our example, the sshd process's PID is 1431. This tool sometimes raises false-positives. Thanks for contributing an answer to Server Fault! This post is probably the most intricate yet due to the fact that we have to manipulate the structure returned by the kernel to userspace. 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. I check the content of buf. This article introduces an unconventional method to hide Linux process from users, with only one line of code: Modify the pid of the process. serveral tips: pathname is from user space, thus copy_from_user magic is required; function type must be long, ive tried int, it returns UINT_MAX - 2 instead of -2 (-ENOENT) Our objective is to hide our reverse shell connection process on the target Linux system in order to avoid detection. 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! Server Fault is a question and answer site for system and network administrators. Its possible to flag a legitimate PID that is not actually cloaked but weve taken measures to limit this risk. 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. Rear wheel with wheel nut very hard to unscrew. Permissive License, Build not available. PIDs are very unpredictable, so we dont want to hardcode one into our rootkit. unhide proc or unhide-linux26 proc for a 64bit system. Were going to combine a few of these techniques now in order to hide certain files and directories from userspace. LO Writer: Easiest way to put line of words into table as rows (list), Book where a girl living with an older relative discovers she's a robot, Including page number for each page in QGIS Print Layout. I have the source code of Kbeast rootkit. Process won't show in the process list. It a match found then, free the kernel buffer kbuf. Linux Stealth Rootkit Process Decloaking Tool sandfly-processdecloak, 4 Ash Street Christchurch, New Zealand 8011. How to draw a grid of grids-with-polygons? We can implement a custom signal handler again (like in Part 3 and Part 5). The Trojan from last year called Hand of Thief failed in its ambitions to be the first banking Trojan for Linux desktops. Usually by hiding them in devious software that looks legitimate and could be functional. Did Dick Cheney run a death squad that killed Benazir Bhutto? 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. So, if we hide directories with the name of the PID we want to keep secret, then these userspace tools wont notice that the process is there! Simply point Sandfly at the hosts you want investigated and well do the rest in seconds. Is my understanding is correct? If this confirms that you have been compromised then your only realistic action is to make a copy of the compromised server to analyse later then reinstall from scratch and recover using known good backups. Hope you enjoyed working through this one - Well Done for making to the end! Its my live server and i host around 20 sites on it. Be warned though, its not as simple as it may sound! 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. Note is small hidden, so, it is not worth countering, tease 1 senior meeting engineer to engage in a prank to play. How often are they spotted? When we get a copy of Drovorub well be sure to add updates to decloak it as well if not seen already. The rough outline of our hook will look like this: Hopefully by this point, the above skeleton makes perfect sense. It contains nothing, therefore it never works. . Can an autistic person with difficulty making eye contact survive in the workplace? How to run a server on port 80 as a normal user on Linux? This is because strlen(hide_pid) will be 0, so the call to memcmp() will always return true. This hides process from all other commands such as ps, top, htop . Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. What can I do if my pomade tin is 0.1 oz over the TSA limit? In the meanwhile the process may have terminated, raising the alert you just saw. This malware is notable for how it loads malicious kernel modules to keep its cryptocurrency mining operations hidden. How do I programmatically determine operating system in Java? Unfortunately, if you're not running a HIDS now, then it's too late to install one. Find centralized, trusted content and collaborate around the technologies you use most. A rootkit is a malicious program that allows administrators to access a computer network at the administrator level. How to constrain regression coefficients to be proportional. 6. We will focus on the 64-bit version, sys_getdents64, for now. @perplex I meant the other way; I think your kernel is too recent; you might need an older one for kbeast. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. The only downside is that we can only hide one PID at a time. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. How can I increase the full scale of an analog voltmeter and analog current meter or ammeter? In my script I am using the system call, example below: os.system ("./myprogram.pl -x 5 > results.out") When I run myscript.py on the server whenever there is os.system call, the command call is visible on the server. Most rootkits/malware use the power of the kernel to hide, they are only visible from within the kernel. It only takes a minute to sign up. Success! Transformer 220/380/440 V 24 V explanation, Replacing outdoor electrical box at end of conduit. Rear wheel with wheel nut very hard to unscrew, Non-anthropic, universal units of time for active SETI. PID 43218 gets hidden from the output of ps - and we didnt even have to try that hard! We do further checks in critical system areas for files loading kernel modules but are hiding this data from view. Thats left as an exercise for you, dear reader! Adore-Ng is a relatively old, open-source, well-known kernel rootkit for Linux, which initially targeted kernel 2.x but is currently updated to target kernel 3.x. 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. It should be clear what the new parts are doing (look for the comments), but if not, try re-reading the paragraph above it. and what maximum damage it can do. This means that, once weve returned the buffer to the user, and some userspace tool (like ls) is looping through the entries just like we have, theyll get to the entry before the one we want to hide, and when it increments its looping variable by d_reclen, it will completely jump over our secret entry. When run, the program will show all clean or PIDs that are suspicious. 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. command using strstr (), it looks for the process_to_hide (H4X0R). It would probably be a good thing to install and run rkhunter. 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. I prefer women who cook good food, who speak three languages, and who go mountain hiking - what if it is a woman who only has one of the attributes? how to move packet from NF_INET_PRE_ROUTING to NF_INET_POST_ROUTING? We can see sys_getdents64 being called with all its arguments and that its written 600 bytes into the buffer we provided. If we dont then the module will start off by hiding every directory on the system. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Which kernel version are you running? 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. 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! Do you see that hidden process every time you run OSSEC? Below is the annotated (and trimmed) output that I got: Okay, this is a bit clearer. Do any Trinitarian denominations teach from John 1 with, 'In the beginning was Jesus'? There is a slight caveat that we will hide all files or directories with the name of the PID were hiding. Sandfly 4.2 Released - Faster, Automatic Discovery. Linux rootkit to hide a PROCESS 328 views Oct 28, 2021 usm durr 197 subscribers 6 Dislike Share Linux rootkit to hide a process. * 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. @mevets My kernel version is 5.3.0-45-generic. To do this, we need yet another linux_dirent64 struct, which we'll call previous_dir, and update it as we loop through everything. 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. 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. rev2022.11.4.43008. Memory rootkits hide in the RAM memory of your computer. As we loop through, we can just increment offset by current_dir->d_reclen so that when current_dir gets redefined at the start of the loop, we will skip over the first struct and move on to the second. Spanish - How to write lm instead of lim? Looking back at include/linux/readdir.c we can see d_reclen used in precisely this way (albeit after being copied into another struct first). using copy_from_user (), buf is copied into a kernel buffer kbuf and then upon detecting the ps||pstree||. In what follows, only the new parts are commented. 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. Should we burninate the [variations] tag? The proper time to install a HIDS is when the server is first installed, and before it is put onto a network. "Used" memory in top larger than the VmSize of all pocesses listed in /proc/? 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.
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