this post was submitted on 08 Jul 2023
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I put up a vps with nginx and the logs show dodgy requests within minutes, how do you guys deal with these?

Edit: Thanks for the tips everyone!

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[–] [email protected] 44 points 1 year ago* (last edited 1 year ago)

A pentester here. Those bad looking requests are mostly random fuzzing by bots and sometimes from benign vulnerability scanners like Censys. If you keep your applications up date and credentials strong, there shouldn’t be much to worry about. Of course, you should review the risks and possible vulns of every web application and other services well before putting them up in the public. Search for general server hardening tips online if you’re unsure about your configuration hygiene.

An another question is, do you need to expose your services to the public? If they are purely private or for a small group of people, I’d recommend putting them behind a VPN. Wireguard is probably the easiest one to set up and so transparent you wouldn’t likely even notice it’s there while using it.

But if you really want to get rid of just those annoying requests, there’s really good tips already posted here.

Edit. Typos

[–] teapot 44 points 1 year ago (1 children)

Anything exposed to the internet will get probed by malicious traffic looking for vulnerabilities. Best thing you can do is to lock down your server.

Here's what I usually do:

  • Install and configure fail2ban
  • Configure SSH to only allow SSH keys
  • Configure a firewall to only allow access to public services, if a service only needs to be accessible by you then whitelist your own IP. Alternatively install a VPN
[–] [email protected] 14 points 1 year ago (1 children)

I would suggest crowdsec and not fail2ban

[–] [email protected] 13 points 1 year ago (1 children)

Seconded, not only is CrowdSec a hell of a lot more resource efficient (Go vs Python IIRC), having it download a list of known bad actors for you in advance really slows down what it needs to process in the first place. I’ve had servers DDoSed just by fail2ban trying to process the requests.

[–] [email protected] 3 points 1 year ago* (last edited 1 year ago) (1 children)

Hi,

Reading the thread I decided to give it a go, I went ahead and configured crowdsec. I have a few questions, if I may, here's the setup:

  • I have set up the basic collections/parsers (mainly nginx/linux/sshd/base-http-scenarios/http-cve)
  • I only have two services open on the firewall, https and ssh (no root login, ssh key only)
  • I have set up the firewall bouncer.

If I understand correctly, any attack detected will result in the ip being banned via iptables rule (for a configured duration, by default 4 hours).

  • Is there any added value to run the nginx bouncer on top of that, or any other?
  • cscli hub update/upgrade will fetch new definitions for collections if I undestand correctly. Is there any need to run this regularly, scheduled with let's say a cron job, or does crowdsec do that automatically in the background?
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[–] [email protected] 23 points 1 year ago (8 children)

Fail2ban and Nginx Proxy Manager. Here's a tutorial on getting started with Fail2ban:

https://github.com/yes-youcan/bitwarden-fail2ban-libressl

[–] [email protected] 3 points 1 year ago

I really wanted to use this and set it up a while ago. Works great but in the end I had to deactivate it, because my nextcloud instance would cause too many false positives (404s and such) and I would ban my own up way too often.

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[–] [email protected] 17 points 1 year ago

I mean, it's not a big deal to have crawlers and bots poking at our webserver if all you do is serving static pages (which is common for a blog).

Now if you run code on server side (eg using PHP or python), you'll want to retrieve multiple known lists of bad actors to block them by default, and setup fail2ban to block those that went through. The most important thing however is to keep your server up to date at all times.

[–] [email protected] 16 points 1 year ago (1 children)

Nothing too fancy other than following the recommended security practices. And to be aware of and regularly monitor the potential security holes of the servers/services I have open.

Even though semi-related, and commonly frowned upon by admins, I have unattended upgrades on my servers and my most of my services are auto-updated. If an update breaks a service, I guess its an opportunity to earn some more stripes.

[–] [email protected] 4 points 1 year ago (1 children)

Why is unattended upgrades frowned upon? Seems like I good idea all round to me?

[–] [email protected] 4 points 1 year ago (1 children)

Mostly because stability is usually prioritized above all else on servers. There's also a multitude of other legit reasons.

[–] [email protected] 10 points 1 year ago (2 children)

All the legit reasons mentioned in the blog post seem to apply to badly behaved client software. Using a good and stable server OS avoids most of the negatives.

Unattended Upgrades on Debian for example will by default only apply security updates. I see no reason why this would harm stability more than running a potentially unpatched system.

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[–] [email protected] 16 points 1 year ago* (last edited 1 year ago) (2 children)

I only expose services on IPv6, for now that seems to work pretty well - very few scanners (I encounter only 1 or 2 per week, and they seem to connect to port 80/443 only).

[–] [email protected] 5 points 1 year ago (2 children)

Must be nice living in a post 1995 country... theres only 1 or 2 ISPs in Australia that support ipv6...

[–] [email protected] 3 points 1 year ago (3 children)

Lol, I have heard some ISP horror stories from the Down Under.

I am fortunate enough that my country's government has been forcing ISPs to implement IPv6 in their backbone infrastructure, so nowadays all I have to really do is to flick a switch on the router (unfortunately many routers still turn off IPv6 by default) to get an IPv6 connection.

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[–] [email protected] 2 points 1 year ago (1 children)

Isn't that akin to security through obscurity... you might want one more layer of defense

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago)

I still have firewall (that blocks almost all incoming connections) and sshguard setup. I also check the firewall logs daily, blocking IPs that I find to be suspicious.

I could probably do better, but with so few scanners connecting to my home server, I have managed to sleep way better than back when I setup a server on IPv4!

Also, even if my home server gets attacked, at least I know that my other devices aren't sharing the same IP with them... NAT-less is a godsend.

[–] [email protected] 11 points 1 year ago

I've been using crowdsec with swag for quite some time. I set it up with a discord notifier. It's very interesting to see the types of exploits that are probed and from each country. Crowdsec blocks just like fail2ban and seems to do so in a more elegant fashion.

[–] [email protected] 9 points 1 year ago

I map them every day.

[–] [email protected] 8 points 1 year ago
  • Turn off password login for SSH and only allow SSH keys
  • Cloudflare tunnel
  • Configure nginx to resolve the real IPs since it will now show a bunch of Cloudflare IPs. See discussion.
  • Use Fail2ban or Crowdsec for additional security for anything that gets past Cloudflare and also monitor SSH logs.
  • Only incoming port that needs to be open now is SSH. If your provider has a web UI console for your VPS you can also close the SSH port, but that's a bit overkill.
[–] [email protected] 8 points 1 year ago (1 children)

I use fail2ban and add detection (for example I noticed that after I implemented it for ssh, they started using SMTP for brute force, so had to add that one as well.

I also have another rule that observes fail2ban log and adds repeated offenders to a long term black list.

[–] [email protected] 2 points 1 year ago (1 children)
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[–] [email protected] 8 points 1 year ago

sometimes I grab popcorn and "tail -f /var/log/secure"

[–] [email protected] 7 points 1 year ago

Ignore them, as long as your firewall is set up properly.

[–] [email protected] 6 points 1 year ago

I use Caddy as a reverse proxy, but most of this should carry over to nginx. I used to use basic_auth at the proxy level, which worked fine(-ish) though it broke Kavita (because websockets don't work with basic auth, go figure). I've since migrated to putting everything behind forward_auth/Authelia which is even more secure in some ways (2FA!) and even more painless, especially on my phone/tablet.

Sadly reverse proxy authentication doesn't work with most apps (though it works with PWAs, even if they're awkward about it sometimes), so I have an exception that allows Jellyfin through if it's on a VPN/local network (I don't have it installed on my phone anyway):

@notapp {
  not {
    header User-Agent *Jellyfin*
    remote_ip 192.160.0.0/24 192.168.1.0/24
  }
}
forward_auth @notapp authelia:9091 {
  uri /api/verify?rd=https://authelia.example
}

It's nice being able to access everything from everywhere without needing to deal with VPNs on Android^ and not having to worry too much about security patching everything timely (just have to worry about Caddy + Authelia basically). Single sign on for those apps that support it is also a really nice touch.

^You can't run multiple VPN tunnels at once without jailbreaking/rooting Android

[–] [email protected] 6 points 1 year ago (1 children)

Any service I have that is public facing is proxied through Cloudflare. I run a firewall on the host that only allows traffic from Cloudflare IPs. Those IPs are updated via a cron job that calls this script: https://github.com/Paul-Reed/cloudflare-ufw I also have a rule set up in Cloudflare that blocks traffic from other countries.

For WAF, I use modsecurity with nginx. It can be a little time consuming to set up and weed out false positives, but it works really well when you get it configured properly.

Some of my applications are set up with Cloudflare Access. I use this with Azure AD free tier and SAML, but it could be set up with self hosted solutions like authentik.

[–] [email protected] 5 points 1 year ago (2 children)

Is everyone using Cloudflare?

[–] [email protected] 3 points 1 year ago

Pretty much, strange in the self-hosted community to have stuff like that happen.

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[–] [email protected] 5 points 1 year ago

I'm using BunkerWeb which is an Nginx reverse-proxy with hardening, ModSecurity WAF, rate-limiting and auto-banning out of the box.

[–] [email protected] 5 points 1 year ago

I've implemented bot blocker and some iptables rate limiting.

[–] Dr_Toofing 5 points 1 year ago (2 children)

These requests are probably made by search/indexing bots. My personal server gets a quite a lot of these, but they rarely use any bandwidth.
The easiest choice (probably disliked by more savvy users) is to just enable cloudflare on your server. It won't block the requests, but will stop anything malicious.
With how advanced modern scraping techniques are there is so much you can do. I am not an expert, so take what I say with a grain of salt.

[–] [email protected] 2 points 1 year ago

The ligitimate web spiders (for example the crawler used by Google to map the web for search) should pay attention to robots.txt. I think though that that is only valid for web-based services.

[–] [email protected] 2 points 1 year ago (1 children)

Fail2Ban is great and all, but Cloudflare provides such an amazing layer of protection with so little effort that it's probably the best choice for most people.

You press a few buttons and have a CDN, bot attack protection, DDOS protection, captcha for weird connections, email forwarding, static website hosting... It's suspicious just how much stuff you get for free tbh.

[–] [email protected] 8 points 1 year ago (3 children)

And you only need to give them your unencrypted data...

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[–] [email protected] 5 points 1 year ago (2 children)

I do client ssl verification.
Nobody but me or my household is supposed to access those anyway.
Any failure is a ban (I don't remember how long for).
I also ban every IP not from my country, adjusting that sometimes if I travel internationally.
It's much easier when you host stuff only for your devices (my case) and not for the larger public (like this lemmy instance).

[–] [email protected] 4 points 1 year ago (3 children)

How do you have this set up? Is it possible to have a single verification process in front of several exposed services? Like as part of a reverse proxy?

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[–] [email protected] 2 points 1 year ago (1 children)

That sounds like an excellent solution for web based apps, but what about services like Plex or Nextcloud that use their own client side apps?

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[–] [email protected] 4 points 1 year ago (1 children)

I use ACL where I add my home/work IPs as well as a few commonly used VPNs IPs as well. Cloudflare clocks known bots for me. Don't see anything in the server logs, but I do see attempts on the CF side.

[–] [email protected] 2 points 1 year ago

I am actually thinking about going back to Cloudflare tunnels. The only reason that I am hesitant is that I do use a fair amount of bandwidth as I host a mastodon server as well as a lemmy one. I don't want to be stuck with a huge bandwidth bill.

[–] [email protected] 3 points 1 year ago (1 children)

Depends on what kind of service the malicious requests are hitting.

Fail2ban can be used for a wide range of services.

I don't have a public facing service (except for a honeypot), but I've used fail2ban before on public ssh/webauth/openvpn endpoint.

For a blog, you might be well served by a WAF, I've used modsec before, not sure if there's anything that's newer.

[–] [email protected] 3 points 1 year ago

I stopped messing with port forwarding and reverse proxies and fail2ban and all the other stuff a long time ago.

Everything is accessible for login only locally, and then I add Tailscale (alternative would be ZeroTier) on top of it. Boom, done. Everything is seamless, I don't have any random connection attempts clogging up my logging, and I've massively reduced my risk surface. Sure I'm not immune; if the app communicates on the internet, it must be regularly patched, and that I do my best to keep up with.

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