Recently, I discovered that SSH of my VPS server is constantly battered as follows.

Apr 06 11:15:14 abastro-personal-arm sshd[102702]: Unable to negotiate with 218.92.0.201 port 53768: no matching key exchange method found. Their offer: diffie>
Apr 06 11:30:29 abastro-personal-arm sshd[102786]: Unable to negotiate with 218.92.0.207 port 18464: no matching key exchange method found. Their offer: diffie>
Apr 06 11:45:36 abastro-personal-arm sshd[102881]: Unable to negotiate with 218.92.0.209 port 59634: no matching key exchange method found. Their offer: diffie>
Apr 06 12:01:02 abastro-personal-arm sshd[103019]: Unable to negotiate with 218.92.0.203 port 16976: no matching key exchange method found. Their offer: diffie>
Apr 06 12:05:49 abastro-personal-arm sshd[103066]: Unable to negotiate with 218.92.0.212 port 49130: no matching key exchange method found. Their offer: diffie>
Apr 06 12:07:09 abastro-personal-arm sshd[103077]: Connection closed by 162.142.125.122 port 56110 [preauth]
Apr 06 12:12:18 abastro-personal-arm sshd[103154]: Connection closed by 45.79.181.223 port 22064 [preauth]
Apr 06 12:12:19 abastro-personal-arm sshd[103156]: Connection closed by 45.79.181.223 port 22078 [preauth]
Apr 06 12:12:20 abastro-personal-arm sshd[103158]: Connection closed by 45.79.181.223 port 22112 [preauth]
Apr 06 12:21:26 abastro-personal-arm sshd[103253]: Connection closed by 118.25.174.89 port 36334 [preauth]
Apr 06 12:23:39 abastro-personal-arm sshd[103282]: Unable to negotiate with 218.92.0.252 port 59622: no matching key exchange method found. Their offer: diffie>
Apr 06 12:26:38 abastro-personal-arm sshd[103312]: Connection closed by 92.118.39.73 port 44400
Apr 06 12:32:22 abastro-personal-arm sshd[103373]: Unable to negotiate with 218.92.0.203 port 57092: no matching key exchange method found. Their offer: diffie>
Apr 06 12:49:48 abastro-personal-arm sshd[103556]: error: maximum authentication attempts exceeded for root from 98.22.89.155 port 53675 ssh2 [preauth]
Apr 06 12:49:48 abastro-personal-arm sshd[103556]: Disconnecting authenticating user root 98.22.89.155 port 53675: Too many authentication failures [preauth]
Apr 06 12:49:51 abastro-personal-arm sshd[103558]: error: maximum authentication attempts exceeded for root from 98.22.89.155 port 53775 ssh2 [preauth]
Apr 06 12:49:51 abastro-personal-arm sshd[103558]: Disconnecting authenticating user root 98.22.89.155 port 53775: Too many authentication failures [preauth]
Apr 06 12:49:53 abastro-personal-arm sshd[103561]: error: maximum authentication attempts exceeded for root from 98.22.89.155 port 53829 ssh2 [preauth]
Apr 06 12:49:53 abastro-personal-arm sshd[103561]: Disconnecting authenticating user root 98.22.89.155 port 53829: Too many authentication failures [preauth]
Apr 06 12:49:54 abastro-personal-arm sshd[103563]: Connection closed by 98.22.89.155 port 53862 [preauth]
Apr 06 12:50:41 abastro-personal-arm sshd[103576]: Invalid user  from 75.12.134.50 port 36312
Apr 06 12:54:26 abastro-personal-arm sshd[103621]: Connection closed by 165.140.237.71 port 54236
Apr 06 13:01:26 abastro-personal-arm sshd[103702]: Connection closed by 193.32.162.132 port 33380
Apr 06 13:03:40 abastro-personal-arm sshd[103724]: Unable to negotiate with 218.92.0.204 port 60446: no matching key exchange method found. Their offer: diffie>
Apr 06 13:11:49 abastro-personal-arm sshd[103815]: Received disconnect from 165.140.237.71 port 50952:11:  [preauth]
Apr 06 13:11:49 abastro-personal-arm sshd[103815]: Disconnected from authenticating user root 165.140.237.71 port 50952 [preauth]
Apr 06 13:19:08 abastro-personal-arm sshd[103897]: Unable to negotiate with 218.92.0.208 port 59274: no matching key exchange method found. Their offer: diffie>
Apr 06 13:33:36 abastro-personal-arm sshd[104066]: Received disconnect from 165.140.237.71 port 50738:11:  [preauth]
Apr 06 13:33:36 abastro-personal-arm sshd[104066]: Disconnected from authenticating user ubuntu 165.140.237.71 port 50738 [preauth]
Apr 06 13:34:50 abastro-personal-arm sshd[104079]: Unable to negotiate with 218.92.0.204 port 44816: no matching key exchange method found. Their offer: diffie>
Apr 06 13:50:32 abastro-personal-arm sshd[104249]: Unable to negotiate with 218.92.0.206 port 27286: no matching key exchange method found. Their offer: diffie>
Apr 06 13:51:58 abastro-personal-arm sshd[104261]: Received disconnect from 165.140.237.71 port 50528:11:  [preauth]
Apr 06 13:51:58 abastro-personal-arm sshd[104261]: Disconnected from authenticating user root 165.140.237.71 port 50528 [preauth]
Apr 06 14:01:25 abastro-personal-arm sshd[104351]: Invalid user  from 65.49.1.29 port 18519
Apr 06 14:01:28 abastro-personal-arm sshd[104351]: Connection closed by invalid user  65.49.1.29 port 18519 [preauth]

As you can see, it is happening quite frequently, and I am worried one might break in at some point. Since SSH access guards users with root-access, it can be quite serious once penetrated. How do I harden against these kind of attacks? Because this is VPS, disabling SSH is a no-go (SSH is my only entry of access). Are there ways to stop some of these attackers?

As always, thanks in advance!

  • tomsh@lemmy.worldEnglish
    8·
    3 hours ago

    In addition to what others say, I also have ntfy notifications on successful login.

  • Gerowen@lemmy.worldEnglish
    20·
    6 hours ago

    I generally do a few things to protect SSH:

    1. Disable password login and use keys only
    2. Install and configure Fail2Ban
    3. Disable root login via ssh altogether. Just change “permit root login” from “no password” to just “no”. You can still become root via sudo or su after you’re connected, but that would trigger an additional password request. I always connect as a normal user and then use sudo if/when I need it. I don’t include NOPASSWD in my sudoers to make certain sudo prompts for a password. Doesn’t do any good to force normal user login if sudo doesn’t require a password.
    4. If connecting via the same network or IPs, restrict the SSH open port to only the IPs you trust.
    5. I don’t have SSH internet visible. I have my own Wireguard server running on a separate raspberry pi and use that to access SSH when I’m away, but SSH itself is not open to the internet or forwarded in the router.
    • k_rol@lemmy.caEnglish
      11·
      1 hour ago

      I vote for wireguard here, I don’t expose anything other than game servers to the internet

  • bizdelnick@lemmy.mlEnglish
    13·
    7 hours ago

    The best way is to disable password login and use SSH keys only. Any further steps are not required, but you may additionally install fail2ban or sshguard.

  • plz1@lemmy.worldEnglish
    4·
    7 hours ago

    Does SSH have to be your only way? Could you deploy something like Tailscale? Can you restrict the allowed IP ranges on SSH with a firewall rule?

  • kylian0087@lemmy.dbzer0.comEnglish
    17·
    13 hours ago

    Configure the firewall with a IP whitelist to only allow connections to ssh be made from your home IP.

    Other then that, disable password logon for ssh and setup up key based authentication.

    • sugar_in_your_tea@sh.itjust.worksEnglish
      3·
      2 hours ago

      Agreed, but be careful about the whitelist. If your home IP changes, you’ll be locked out until you update it, so you should consider an IP range if that’s a possibility for you. Likewise, if you’ll be accessing it from multiple locations (say, a family member’s house), then make sure to add those as well.

  • Phoenixz@lemmy.caEnglish
    425·
    21 hours ago

    Move the ssh port to higher ranges, 30-60000. That alone will stop 99% of the attacks

    Disable root logins, now usernames must be guessed too which will make success even lower

    Then require SSH keys

    At that point it’s like being in a nuclear fallout nshelter behind a 3 meter thick steel door and you can hear some zombies scratching on the outside… I’m not worried about any of that shit

    • Possibly linux@lemmy.zipEnglish
      42·
      2 hours ago

      Changing the port is a total waste of time

      Changing the port is just like putting a picture of a window on your door. Harden SSH properly and don’t waste time with security via obscurity

      • AustralianSimon@lemmy.worldEnglish
        2·
        1 hour ago

        I think the point behind it is to waste the sniffers time sniffing for ports that it could be using to be making attempts.

        Its not a security thing, it’s just increasing the cost to snoop.

      • sugar_in_your_tea@sh.itjust.worksEnglish
        4·
        2 hours ago

        That’s not true.

        Security through obscurity isn’t real security, sure, but it does a lot to reduce the noise in the logs so you can see the more real attacks. Hardening SSH properly is certainly more important, but changing the port also has value.

    • null_dot@lemmy.dbzer0.comEnglish
      61·
      14 hours ago

      This is what I do. Changing the port to a higher number will prevent almost all bots.

      I understand that obscurity is not security but not getting probed is nice.

      Also ssh keys are a must.

      I do log in as root though.

      However, I block all IPs other than mine from connecting to this port in my host’s firewall. I only need to log in from home, or my office, and in a crisis I can just log in to OVH and add whitelist my IP.

      • sugar_in_your_tea@sh.itjust.worksEnglish
        2·
        2 hours ago

        I do log in as root though.

        Don’t do that. You’re one local piece of malware away from getting your server pwned. Logging in as an unprivileged user at least requires another exploit on the server to get root permissions.

  • Xanza@lemm.eeEnglish
    52·
    23 hours ago
    1. Disable passwordless login.
    2. Disable password login.
    3. Require SSH keys
    4. Move SSH port to non-standard port
    5. Reject connections to port 22
    6. Install and enable fail2ban

    About the best you can do.

          • sugar_in_your_tea@sh.itjust.worksEnglish
            21·
            4 hours ago

            Fail2ban blocks IPs that fail to connect repeatedly. A honeypot pretends fails worked and gives them a worthless environment to try to exploit. The purpose of fail2ban is to block attacks, the purpose of a honeypot is amusement and to waste attackers’ time.

            • ILaughBecauseFunny@feddit.dkEnglish
              2·
              4 hours ago

              I understood the comment as “leave the port open to ssh, to easily allow fail2ban to hit the ip’s before they get through your full port range.” But thanks for the elaborate answer :)

              I agree, what you described is much more work ;)

    • markstos@lemmy.worldEnglish
      113·
      23 hours ago

      Using a nonstandard port doesn’t get you much, especially popular nonstandard ports like 2222.

      I used that port once and just as much junk traffic and ultimately regretted bothering.

      • friend_of_satan@lemmy.worldEnglish
        161·
        23 hours ago

        My experience running several ssh servers on uncommon nonstandard ports for over 10 years has been that it has eliminated all ssh brute forcing. I don’t even bother with fail2ban. I probably should though, just in case.

        Also, PSA: if you use fail2ban, don’t try tab completing rsync commands without using controlmaster or you will lock yourself out.

      • irmadlad@lemmy.worldEnglish
        51·
        23 hours ago

        My two cents: Using a nonstandard ssh port is good for dumping bots. True, you can easily do a port scan against a server and easily find all open ports nbd. But most off-the-shelf bots are looking for standard ports to penetrate. I know that when I format and reinstall the test server, as soon as I change the ssh port, bot noise goes down significantly. So, for a simple config edit and about 2 minutes of time, it seems worth the effort. It’s just one layer tho. And yes, it goes without saying to pick a port other than 22, 222, 2222, etc.

          • sugar_in_your_tea@sh.itjust.worksEnglish
            2·
            1 hour ago

            Oh, that one’s fine. Everyone knows that 5-digit ports add extra security, which is why WireGuard runs on port 51820 by default. You can verify this by checking the max port number, which is also 5-digits, computers just aren’t powerful enough to crack 6-digit port numbers, so Linux hasn’t bothered increasing it. /s

      • cmnybo@discuss.tchncs.deEnglish
        51·
        23 hours ago

        It gets rid of most of the login attempts for me. I don’t use a popular port though. Pick a 5 digit port so they have to put in some effort to find it.

    • sugar_in_your_tea@sh.itjust.worksEnglish
      2·
      1 hour ago

      harden sshd

      More details:

      • require keys to login
      • don’t allow login as root

      That should be plenty, but you could go a bit further and restrict the types of algorithms allowed (e.g. disallow RSA if you’re worried about quantum attacks). For this, I recommend a subtractive config (e.g. HostbasedAcceptedAlgorithms=-rsa-*). This is way over the top since an attacker is unlikely to attack the cipher directly, but it could be part of an attack.

    • dev_null@lemmy.mlEnglish
      3·
      5 hours ago

      Your answer to “how to harden SSH?” is “harden SSH”?

      I know your two other points gave concrete suggestions, but it’s pretty funny you suggested to “harden sshd” when that is what OP is asking how to do.

      • zr0@lemmy.dbzer0.comEnglish
        1·
        51 minutes ago

        Yeah, I see your point. No use to repeat the same you can read in other comments or in those 274772 guides online. I was trying to imply to just generally harden ssh because then brute-force attempts should be no issue, unless you log everything and the disk space gets maxed out :D

  • irmadlad@lemmy.worldEnglish
    18·
    22 hours ago

    OP, here is what I do. It might seem overboard, and my way doesn’t make it the best, or the most right, but it seems to work for me:

    • Fail2ban
    • UFW
    • Reverse Proxy
    • IPtraf (monitor)
    • Lynis (Audit)
    • OpenVas (Audit)
    • Nessus (Audit)
    • Non standard SSH port
    • CrowdSec + Appsec
    • No root logins
    • SSH keys
    • Tailscale
    • RKHunter

    The auditing packages, like Lynis, will scour your server, and make suggestions as to how to further harden your server. Crowdsec is very handy in that it covers a lot of ‘stuff’. It’s not the only WAF around. There is Wazuh, Bunkerweb, etc. Lots of other great comments here with great suggestions. I tend to go overboard on security because I do not like mopping up the mess after a breach.

    ETA: just looked up one of your attackers:

    218.92.0.201 was found in our database! This IP was reported 64,044 times. Confidence of Abuse is 100%: ISP CHINANET jiangsu province network Usage Type Fixed Line ISP ASN AS4134 Domain Name chinatelecom.cn Country China City Shanghai, Shanghai

    busy little cunts.

    • sugar_in_your_tea@sh.itjust.worksEnglish
      2·
      1 hour ago

      It’s absolutely overboard, and you can get 99% of the way there with this:

      1. WireGuard config (Tailscale in your case)
      2. Bind SSH to WireGuard IP only (so no public SSH port)
      3. SSH keys only, and disable root login over SSH

      That will require breaking WireGuard and openSSH’s key-based authentication, which just isn’t happening. The rest looks like mostly auditing. Even a firewall isn’t necessary if no ports are accessible anyway (i.e. everything only accessible over Tailscale), and you can just configure iptables to block everything on the WAN IP and call it a day.

      • irmadlad@lemmy.worldEnglish
        2·
        16 minutes ago

        sugar_in_your_tea @sh.itjust.works

        It’s nice to be commented by someone famous.

        Open up the window, let some air into this room I think I’m almost chokin’ from the smell of stale perfume And that cigarette you’re smokin’ 'bout scare me half to death Open up the window, sucker, let me catch my breath

        • sugar_in_your_tea@sh.itjust.worksEnglish
          1·
          3 minutes ago

          Mama told me not to come.

          Fun fact, my usernames on Reddit (I would cycle them every couple of years) were all Three Dog Night lyrics, so I continued the theme on Lemmy.

          Thanks for noticing. 😀

  • CondorWonder@lemmy.caEnglish
    631·
    1 day ago

    We can’t ever stop this kind of stuff, but with something like fail2ban you can set it up to block on too many failures.

    Really though - ensuring your system is kept up to date and uses strong passwords or use a SSH keys is the best defence. Blocking doesn’t prevent them from trying a few times. Moving SSH to a non standard port will stop most of the automated attacks but it won’t stop someone who is dedicated.

    • Lucy :3@feddit.orgEnglish
      231·
      1 day ago

      Move SSH to non-standard port, make endlessh use the default port. Only use SSH keys. Only allow correct users (so eg. your user and git/forgejo). Use fail2ban to aggressively ban (redirect to default port, so 22) and report to abuseipdb everything that fails to authenticate first try (wrong user, password instead of key), has non-compatible ciphers (generally, only allow TLS1.3 etc.), or fails in any other way. Just be sure that if you accidentally get banned yourself (eg. Ctrl+C-ing during authentication), you can use another IP (eg. force v4) for connecting.

      • cron@feddit.orgEnglish
        102·
        1 day ago

        Nice list of suggestions, but implementing all of them feels a little over-the-top.

        • Lucy :3@feddit.orgEnglish
          9·
          21 hours ago

          Tbh, I myself still have SSH on port 22. Firstly, because I’m lazy, and secondly … yeah that’s it. I’m honestly just lazy. But spam bots trying office/cookie123 are not a real threat, and anyone trying to actually target me will either have somehow acquired my key + password, use one of the probably many security issues that exist in the dozen services I selfhost, social engineer me into doing something (not saying I’ve given out my (old) KeePass password once, but it could be, as love makes blind (I still love her)), or just smash my kneecaps until I give out everything.

        • Lucy :3@feddit.orgEnglish
          1·
          21 hours ago

          But remember, on a third device. Not the one where your KeePass DB is one fingerprint away, and your private SSH key too.

    • someacnt@sh.itjust.worksOPEnglish
      1·
      19 hours ago

      Thanks, I will try fail2ban. I am using ED25519 for ssh keys, it seems like it’s the best defense on the ssh side. Do you happen to know why this kind of attack is so prevalent?

      • WhyJiffie@sh.itjust.worksEnglish
        2·
        16 hours ago

        I’m not them, but among other reasons they are looking to build botnets (cryptomining, dosing, mass crawling), and they are searching for hosts with low security (or if you just made a mistake)

  • BrianTheeBiscuiteer@lemmy.worldEnglish
    30·
    1 day ago

    In addition to other advice you could also use SSH over Wireguard. Wireguard basically makes the open port invisible. If you don’t provide the proper key upfront you get no response. To an attacker the port might as well be closed.

    Here’s at least one article on the subject: https://rair.dev/wireguard-ssh/

    • NekuSoul@lemmy.nekusoul.deEnglish
      4·
      20 hours ago

      Exactly. No root login and no password login will do just fine as basic measures, but after that Wireguard is perfect tool for this, no weird rituals required and also quite useful for any other services you don’t want and/or need to expose to the internet as well.

      • sugar_in_your_tea@sh.itjust.worksEnglish
        1·
        1 hour ago

        Just remember that you’ll only be able to SSH in w/ a device that’s already configured for WireGuard. So if you’re at a friend’s house and haven’t set up your phone to do it yet, you’ll be forced to use the VPS console to get in. Make sure this is what you want before you do it.