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Dealing with Intruders?
drakyri asks: "I've been running a server for a small company for a few months. Recently, the number of attempted intrusions has jumped from about one every week to several per day - and these are only the really obvious attempts, like idiots who try to log in as root from the outside.
The problem is that I'm not sure what to do about this. I've got their IP addresses and can usually tracert their ISP's - is there an accepted type of letter to send them without seeming like one of the corporate cease-and-desist gnomes?"
The accepted way is to send an email to abuse@ or to the abuse contact listed by ARIN for the netblock you are trying to lart.
http://www.arin.net
or lookup the RADB abuse contact
http://www.dnsstuff.org
I have also been seeing these kinds of "attacks" the last few weeks on a server which I admin. Usually attemts to login via ssh to well-known accounts (such as root).
The site is not a high-profile site by any means but rather a home for some personal projects. I just wrote it of as the script-kiddy attemt de jour but it's interesting to see that others experience the same thing.
you deal with the firewalls,
let your lawyers deal with crap like this
Just ignore them. Focus on keeping your server software up to date and staying informed of possible security issues instead of waisting time trying to track down instrusion attempts.
These two will detect most automatic attempts and then add the IP's to a drop list on your Linux firewall. www.snort.org. Guardian is listed under 'other tools'
I always write a really "nice" letter to the ISP of the intruder, where I explain the problem, and that it is causing my customers trouble and that it eats up valuable bandwidth. I ask them to take action, and if not, that I'll have to proceed further (never been needed once). I send the email from the admin account, sign it with my name + admin at my system and then I attach the logs pertaining the intrusion attempt.
... atleast nowadays), mostly for the more serious attempts (doing multiple attempts, different attempts, etc).
:)
So far, all of these "cease and desist" letters has resulted in action on the ISPs part, and in 50% of the cases, their admins write me back and give me feedback on the problem.
Ofcourse, I don't do this for every attempt (all depending on my mood
The worst (or craziest?) attempt yet was by some nut who portscanned the system, port by port from start to finish. I actaully managed to get hold of the owner of the computer system that was scanning me and phoned him. Quite a hilarious experience. Needless to say, the portscanning stopped
I had confidence in my setup, and no server I had control over was, to my knowledge, ever compromised.
We never had any sensitive data outside the firewall, anyway.
On two occasions it got serious (if an easily beaten DOS attack can be called serious) and even then it was only for 20 minutes or so. Our ISP (being a large telecom) was champing at the bit to go after people we had even a small scrap of evidence against, so on those two occasions we simply handed what information we'd gleaned to them, and they let out the dogs.
At some stage, you've got to stop worrying and learn how to love the internet!
Personally I tend to ignore the scans for ssh and so forth, as they're just SYN-packets and doesn't consume too much of my resources. Call me a lazy/non-caring bastard. However, it would surely be nice to send off a message to the ISP, as the machines the scans are originating from are probably cracked too.
.
.. it's days since the last virus from you! Keep up the good work!"
.. and so forth.
:)
I tend to report viruses. I grep my logs daily for viruses from various norwegian ISPs, to the mailserver I admin for my company. During the last five months I've sent daily virus reports to the largest ISP in norway, and they tend to reply within one business day - having notified their customer about the infection. If the customer gets several 'heads up' messages from the ISP without removing the virus, they get their port 25 access filtered until they've confirmed that they've removed the virus.
I tend to send emails such as this.
"
Hi there.
I've got several viruses from your customers today, and would appreciate it if you could notify your customers about the virus infections they probably have.
Here are the relevant snippets from my logs:
Virus: Netsky.B
Received: from at
Virus: Bagle.C
Received: from at
All timestamps on the server are NTP-sync'ed against
Thanks for your time
"
Recently I've also included a more personalized
"Oh, and I have to commend your ISPs efficiency, as since march - you've managed to reduce the number of virus sending users to us from about per day, to this
You could probably just adapt what I'm writing to something saying that a customer of theirs probably has been cracked, and that they are currently scanning for
If it's the actual cracker that's stupid enough to use his own computer, he'll get scared enough if they contact him telling him that his computers has been abused by others to scan people -- and will probably quit doing it.
"Rune Kristian Viken" - http://www.nwo.no - arca
or you'll spend half your time at work writing abuse letters. My logs at work show a constant barrage of windows attacks ( yes, code red is still there), 137 scans, numerous login hacks for any number of OS's, port scans that increment by 1 each time, etc. Sometimes it slows down. I am beginning to just consider it background noise. Just the cost of doing business on the web. As long as the probes arent massive or working, I just note and ignore. I only have so much time for this - it keeps me from downloading all that porn!
This kind of stuff is all over the place. Odds are most of these are automated worms and similar crap. Unless it's really a concerted attack on your machines, as opposed to random scanning, it's not worth the effort to do anything about it except maybe firewall the IP.
try http://www.mynetwatchman.com/ works like a champ for me.
the system automatically sends a warning to the isp
mid july or so there were a bunch of random automated-looking and weak looking ssh login attempts all over the place ....
....
threads on the full disclosure mailing list archives and dslreports forums about that
wonder if this is what the topic poster was encountering?
Be sure though to include *all* relevant log files too. I've sent a couple of mails in the past to ISPs and i think i got a response from about 50% of the ISPs contacted, from which only one responded once by saying they contacted the individual and took appropriate actions ... whatever that may mean.
You'd be better off configuring your security better though.
Keep in mind that those IP's could be spoofed however, so without something a little more substantial than an IP addy, you are likely to be ignored by most major isp's.
well, if you decide to write to ISP, don't write letter in which you accusing but ask ISP for help to investigate and be polite.
/ss
Honeypots should not be taken lightly. They are a legal hazard. You knowingly operate a vulnerable machine which is connected to the Internet. If the damage isn't restricted to your own systems, you're partially responsible and probably liable for other people's damages.
You said, YOU are running a server for ONE client. Who is it that needs SSH access to the machine - YOU. What i would do is limit access to port 22 to IP adresses I am going to use. Add your normal internet adresses to the list (like your ISPs IP-block, work, girlfriends isp, ...) And of course you need to add a machine that is alwas up and has no such firewall restrictions (i.e. shell access to your server at home, i know you have one ;-)). This way you can login to the server from your most common locations, and login indirectly to the server using another box as "proxy" in case you are on vacation sitting in an internet-cafe.
i think it's also good practice to generally disallow direct root-logins in ssh-config and only allow shell users having group wheel to su to root.
Look up HTB on the net (Heuristic Token Bucket) - a firewall rule that limits network abuse while not obstructing normal network usage - every IP gets a pool of "tokens". One token is removed from the pool when a packet is sent, packets won't be sent as long as the pool is empty, but it gets refilled at constant, slow rate, until it's "full" again. So a user can download, say, 500K in one rapid burst at maximum network capacity, then his connection bandwidth goes down to some 5K. If he waits 100s he will be able to get 500K in similar burst again. This way, one page loads really fast. User reads the page, goes back, loads another one (minute later) very fast again. A loser who keeps reloading, exceeds his 500K bucket content in 2-3 reloads and then gets a constant drip of 5K upstream, hardly disturbing the others.
Anagram("United States of America") == "Dine out, taste a Mac, fries"
Don't bother, the real crackers are probably usings some lusers box to launch the attack from. You're just warning the person who didn't secure their box, and they're not likely to understand why you are telling them they are attacking your box.
All those moments will be lost in time, like tears in rain.
Don't you use a firewall? You can't attempt to log in remotely if you're blocking the typical remote access ports -- SSH, telnet, etc.
So you've got a machine sitting on the internet, home to a million and one active worms, and are surprised that it gets scanned constantly?
Don't bother with the abuse reports -- more than likely it's just worm activity from computers whose clueless owners don't realize have been infected. A more recent one attempts SSH logins, which may be what you're seeing.
It it was a _real_ crack attempt then you:
1: Wouldn't know about it.
2: Would be unable to pin it down. It would be bounced through several victim networks, so your ability to see where it's "coming from" is really just the last victim machine in the chain.
Third possibility is script kiddies, in which case you would know about it and where they were coming from, but they would have no chance of success unless you are unwilling to keep up on patches and follow basic security practices like decent passwords.
Best would be to close off remote-login ports altogether. If you need remote login then block for all but the address range you'd be coming from. If you need remote access from random locations, then at least consider using a heavily locked down system (e.g.: OpenBSD) or work _really hard_ to get your systems firewall/logging/etc. set up well.
One OpenBSD/pf feature you might be interested in (also available from other systems) is the ability to tie Snort into the pf ruleset so that remote scanners, once detected, are ignored.
"But actually trying to use m4 as a general-purpose langage would be deeply perverse" --ESR
In my opinon, Tom Hudson's way of dealing with these critters, is far more entertaining, than just ignoring them.
This is really good advice, but you can do more. :-)
Most ISPs really appreciate the complete header of the mail, and sometimes even the body in case of spam. First of all it adds to the authenticity, and second they'll be able to forward your complaint to the responsible ISPs if you had too much beer while reading a spoofed header (more so for spam than virus mails). Some ISPs are quite helpful in this regard.
To aid in identifying the correct abuse addresses I can recommend the hinfo utility as a complement to whois. Oh and if you're stuck with a standard whois, consider replacing it with the one made by Marco d'Itri - it's the default in Debian, and has the ability to guess the correct whois hosts to ask.
zWhat would an EWOULDBLOCK block, if an EWOULDBLOCK could block would? -- me
1) Tripwire is a file integrity checker. I suppose you mean portsentry or similar. 2) Automatic firewalling a VERY bad idea. Remember that most modern scanning techniques do not require a full TCP connection, and are therefore eminently spoofable. Not imagine someone spoofing a syn scan from the IPs of google.com. BOOM! No more google for you, you just firewalled it off yourself. BOOM! No more slashdot. BOOM! No more quake server. You get the idea.
Pathman, Free (as in GPL) 3D Pac Man
Yeah I know the gentleman's approach.
I don't subscribe to it. I look at it like this:
To drive a car, you need a licence. You have to follow rules. You drive on the correct side of the road. You don't drink and drive. You obey the speed limit. And why do we have to follow the fules? It's because there are other people who also want to use the road, and therefore all drivers have a responsibility to ensure that the safety of others is protected.
Sounds like common sense, right? Well the same should apply to placing computers on the internet. If you want to have viruses and backdoors and worms etc running on your home PC, then fine. Whatever. But if you put your home PC on the internet and take absolutely no fucking responsibility for what you are doing then you are waiving all rights you have over the the safety of your computer. If your computer now pisses me off, I'll 'smbdie' it off the internet. If you're fine with all the rest of the shit that's infecting your PC, then you don't really have any right to complain about me rebooting it once every 5 minutes. And yes I'm doing everyone a service. Firstly, the computer is on the internet for less time than it otherwise would have been, so there's less chance of others being infected. Also, the idiot who owns the computer will be far more likely to do a complete re-install, or at least get a god-damned virus checker and get Windows up-to-date.
Do you know how many people come bitching and complaining to me about their PC being rooted, and when I boot it up find that they're running Windows 2000 SP1 and NO virus protection at all? It's not good enough. And the only ways to get them to take responsibility for their computer are:
a) Legislate. No-one wants legislation covering their computer. It will screw things up for the responsible among us and have no effect on the rest.
b) Make it so unconfortable to run an unprotected computer that they get the hint and protect it.
Having said all this, I know most people will still disagree with me. That's fine. Be angels. Just keep your damned computer secure and you've got nothing to worry about.
In some (these days it may even be most) cases the machine that is doing the attacking has been compromised and hijacked by the cracker. So the 'owner' of that machine may not know that there machine is contributing to global chaos that is the internet. So you might not want to send them a note blasting them (though they are or were running a machine that wasn't patched, whatever). Sometimes machines slip through the cracks and sites with really good security policies and dedicated security people get 0wned, so being polite is generally a good policy. How would you like to get a note that insults berates, humiliates you, instead of someone saying that your machine appears to have been attacking thier machine and could you look into it. This way the person is grateful for you pointing out that there machine was compromised and is more likely to let you know what happened. At least this has been my experience.
When she found out about attacks and attempted intrusions, she got on the phone with the netblock owner and gave them an earful and followed up until something happened, even if it was only a small improvement. If need be, she reported it to the police and was even able to convince them that crime was an area of their responsibility even if they did not currently have the expertise.
The problem with your suggestion is that human response doesn't scale. At her average low of 15 mins per day dealing with the problem manually or socially, the rate of intrusions only has to increase 32-fold before it takes up an entire 8-hour normal working day. How many thousands of network admins are you going to hire to handle a DDoS attack from 100K sources? There is no limit to the number of owned Windows boxes out there.
It doesn't scale and it doesn't help. It is far better to spend your network admin's time on making your systems ever more impervious to attack, and if she has any time left over, to teach others how to do likewise. Ultimately, if all sites are securely tied down then it doesn't matter what the cracker kiddies are doing.
"The question of whether machines can think is no more interesting than [] whether submarines can swim" - Dijkstra
Agreed.
A few years ago in my last job, we got hit with one of those viruses that hacks your web site (IIS of course) and modifies the home page to include bad words. We actually got the FBI involved.
I got to talking with the agent and he basically said, unless someone actually intrudes into your system, you have no recourse. Atempts are one thing, actual intrusions are something else. Also, most likely, the activity you're seeing is viruses, not someone actively trying to break-in. Just keep your systems secure and patched and keep an eye on them.
Self awareness - try it!
Data integrity is more important than catching them. Rememeber that first.
5 708681/104-7409931-6853536?v=glance
1) Make notes about what you've found
2) Report the the abuse as per the WHOIS info for the offenders
3) Block their IPs at your border
If you're using a firewall, great. If not--get one.
If you haven't read Frisch's "Essential System Admnistration" read it:
http://www.oreilly.com/catalog/esa3/index.html
If you haven't read Stephen Northcutt's "Network Intrusion Detection" you should probably give it a good read as well:
http://www.amazon.com/exec/obidos/tg/detail/-/073
There are some good articles all over the web regarding Linux security. A few google searches will help uncover them.
Patch. It's not just for Windows.
Limit services with ACLs and host restriction.
Harden your system by partitioning read/write slices away from static mountpoints where your binaries are by mounting the read only ones as read only.
chattr +i on your binaries--makes it tougher for skript kiddies.
Talk to other admins--every day is a school day.
AND
Face the fact that you're not as smart as the crackers so you just have to create layers of security that keep you from being an easy target.
I might know what I'm talkin' about, but then again, this is Slashdot...
What the hell! Why not?
::ffff:203.186.65.92 ::ffff:203.186.65.92 port 4570 ssh2 ::ffff:217.115.83.1 ::ffff:217.115.83.1 port 39378 ssh2 ::ffff:217.115.83.1 ::ffff:217.115.83.1 port 39462 ssh2 ::ffff:217.115.83.1 ::ffff:217.115.83.1 port 39609 ssh2 ::ffff:217.115.83.1 ::ffff:217.115.83.1 port 39742 ssh2 ::ffff:217.115.83.1 ::ffff:217.115.83.1 port 39878 ssh2 ::ffff:217.115.83.1 port 40005 ssh2 ::ffff:217.115.83.1 port 40145 ssh2 ::ffff:217.115.83.1 port 40277 ssh2 ::ffff:217.115.83.1 ::ffff:217.115.83.1 port 40412 ssh2 ::ffff:217.115.83.1 ::ffff:217.115.83.1 port 49595 ssh2 ::ffff:217.115.83.1 ::ffff:217.115.83.1 port 49726 ssh2 ::ffff:217.115.83.1 ::ffff:217.115.83.1 port 49861 ssh2 ::ffff:217.115.83.1 ::ffff:217.115.83.1 port 49983 ssh2 ::ffff:217.115.83.1 ::ffff:217.115.83.1 port 50117 ssh2 ::ffff:217.115.83.1 port 50257 ssh2 ::ffff:217.115.83.1 port 50398 ssh2 ::ffff:217.115.83.1 port 50546 ssh2 ::ffff:217.115.83.1 ::ffff:217.115.83.1 port 50678 ssh2 ::ffff:202.129.52.50 ::ffff:202.129.52.50 port 3258 ssh2
Aug 12 05:08:28 pokey sshd[7534]: Illegal user test from
Aug 12 05:08:31 pokey sshd[7534]: Failed password for illegal user test from
Aug 12 10:51:33 pokey sshd[7615]: Illegal user test from
Aug 12 10:51:35 pokey sshd[7615]: Failed password for illegal user test from
Aug 12 10:51:39 pokey sshd[7617]: Illegal user guest from
Aug 12 10:51:41 pokey sshd[7617]: Failed password for illegal user guest from
Aug 12 10:51:48 pokey sshd[7619]: Illegal user admin from
Aug 12 10:51:50 pokey sshd[7619]: Failed password for illegal user admin from
Aug 12 10:51:54 pokey sshd[7621]: Illegal user admin from
Aug 12 10:51:57 pokey sshd[7621]: Failed password for illegal user admin from
Aug 12 10:52:01 pokey sshd[7623]: Illegal user user from
Aug 12 10:52:03 pokey sshd[7623]: Failed password for illegal user user from
Aug 12 10:52:10 pokey sshd[7625]: Failed password for root from
Aug 12 10:52:16 pokey sshd[7627]: Failed password for root from
Aug 12 10:52:23 pokey sshd[7629]: Failed password for root from
Aug 12 10:52:27 pokey sshd[7631]: Illegal user test from
Aug 12 10:52:29 pokey sshd[7631]: Failed password for illegal user test from
Aug 12 11:01:41 pokey sshd[7659]: Illegal user test from
Aug 12 11:01:44 pokey sshd[7659]: Failed password for illegal user test from
Aug 12 11:01:48 pokey sshd[7661]: Illegal user guest from
Aug 12 11:01:50 pokey sshd[7661]: Failed password for illegal user guest from
Aug 12 11:01:54 pokey sshd[7663]: Illegal user admin from
Aug 12 11:01:57 pokey sshd[7663]: Failed password for illegal user admin from
Aug 12 11:02:01 pokey sshd[7665]: Illegal user admin from
Aug 12 11:02:03 pokey sshd[7665]: Failed password for illegal user admin from
Aug 12 11:02:07 pokey sshd[7667]: Illegal user user from
Aug 12 11:02:10 pokey sshd[7667]: Failed password for illegal user user from
Aug 12 11:02:16 pokey sshd[7669]: Failed password for root from
Aug 12 11:02:22 pokey sshd[7671]: Failed password for root from
Aug 12 11:02:29 pokey sshd[7673]: Failed password for root from
Aug 12 11:02:33 pokey sshd[7675]: Illegal user test from
Aug 12 11:02:35 pokey sshd[7675]: Failed password for illegal user test from
Aug 12 12:23:19 pokey sshd[7703]: Illegal user test from
Aug 12 12:23:22 pokey sshd[7703]: Failed password for illegal user test from
Aug 12 12:23:26 pokey sshd[7705]: Illegal user guest from
Just submit your logs to dshield.org and they will forward your complaints to the proper admin.
Apparently there is a lot of talk here about involving law enforcement, the law, etc.
What a lot of you don't know, which I learned via hard knocks, was that unless you are a large corporate entity with gross yearly earnings in excess of $500k, there is NOTHING that you can do with any judge, law enforcement, or the FBI. They simply tell you to "deal with it".
This is why the issues of hacking and open spam relays, and all the other jazz will never go away, because it's not profitable or should I say; "chargable" under current statutes.
Good luck!
All content in this message is copyright (c) 2008. All rights reserved. RIAA is prohibited here.
So, being a good guy, I never respond in kind (I could, but 1) it's wrong, 2) it affects more than just the target and 3) I don't feel like going to pound-me-in-the-ass prison), I just log every single packet I can, and when the attack is over find the worst offenders (typically the packets are not spoofed) and use Spamcop and whois to find the responsible parties for each one, and send them all an email.
Many (most?) emails elicit an automatic response.
Perhaps 10% get a personalized response, but usually this response says that I should contact the ISP of the offender (when in fact that's exactly what I'm doing.) Perhaps half of the responses I do get say they'll do something about it, which is good -- usually these are compromised drone/zombie machines, and need cleaning anyways.
Quite often, the attacker is stupid enough to ping my machine from his home machine (so he can see how it's going), not thinking I'll notice that. When this happens, I can also email his home ISP, the people who really know who he is, and the people who can really hit him where it hurts. Except that they ignore my email too, and if they do email me back, they just tell me that the attack did not come from their ISP so they can't do anything, or there's no proof that the pinging is related to the attack.
Phone calls are much more effective than emails, but you really need to make them during the attack for them to take them seriously. And often the attacks happen outside of business hours, so there's nobody to call. And they're very time consuming.
Though I did succeed in nailing at least one guy. He was in Romania, and he messaged me a few weeks after the attack basically pleading with me that it wasn't him, but his brother using his computer. Apparantly the police (in Romania) were questioning him, and one of the things they showed him was my email. The police had never contacted me -- I'm guessing that my email was just one of many pieces of evidence they had against the guy. I felt a bit bad for him, but not that bad. Not that I had any control over what was happening to him at that point -- it was out of my hands the moment I sent my email.
So, if it happens again, I'll do the same thing. I know it's not likely that anything substantial will come from my emails, but there's still a chance. Every time it happens, I know I nail at least some of his compromised machines, and have a chance at getting him. I'll win eventually -- either that, or he'll hit puberty, in which case we both win.
this will only suppress people trying to get into your various info servers (telnet, ftp etc...) you will still get the vast script kiddie assault every day on port 80. you can allow people you want to connect to you on vpn or other services by adding their static ip to the file.
/usr/bin/mail -s "tcpd\: %u@%h[%a] fingered me!" root) & \
/bin/echo "Eat a dog poop. You are not welcome to use %d from %h..."
hosts.allow
#
# hosts.allow This file describes the names of the hosts which are
# allowed to use the local INET services, as decided
# by the '/usr/sbin/tcpd' server.
#
# Prevent those with no reverse DNS from connecting.
ALL : PARANOID : RFC931 20 : deny
# Allow anything from localhost. Note that an IP address (not a host
# name) *MUST* be specified for portmap(8).
ALL : 127.0.0.1 : allow
# internal ip
ALL : 192.168.1.100 : allow
ALL : 192.168.1.200 : allow
ALL : 192.168.1.201 : allow
ALL : 192.168.1.202 : allow
ALL : 192.168.1.203 : allow
ALL : 192.168.1.204 : allow
ALL : 192.168.1.205 : allow
ALL : 192.168.1.206 : allow
ALL : 192.168.1.207 : allow
ALL : 192.168.1.208 : allow
ALL : 192.168.1.209 : allow
ALL : 192.168.1.210 : allow
# other people you like go here
ALL : 00.000.000.00 : allow
# You need to be clever with finger; do _not_ backfinger!! You can easily
# start a "finger war".
fingerd : ALL \
: spawn (echo Finger. | \
: deny
hosts.deny
#
# hosts.deny This file describes the names of the hosts which are
# *not* allowed to use the local INET services, as decided
# by the '/usr/sbin/tcpd' server.
#
# The portmap line is redundant, but it is left to remind you that
# the new secure portmap uses hosts.deny and hosts.allow. In particular
# you should know that NFS uses portmap!
# The rest of the daemons are protected.
ALL : ALL \
: severity auth.info \
: twist
not that i'm an expert or anything. But when i've found others doing ill/breaking the law on the net and informed their ISP... The ISP is unwilling to do anything. Unless your the cops with a warrent they do nothing, and if you are the cops with one, all they will do is give you info on the person. The ISP won't do diddely. I Think they should just like you but they won't and don't.
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