[strongSwan] How to block Netstat attacks from VPN users?

Noel Kuntze noel.kuntze at thermi.consulting
Mon Oct 14 21:47:10 CEST 2019


Hello Houman,

> Depends on what exactly you're doing on your server. It's not possible to give you a generalized answer.

That's what I think.

Am 14.10.19 um 20:49 schrieb Houman:
> Hello Noel,
>
> I just tried the suggested solution below and sadly it blocks the entire VPN.
>
> iptables -I FORWARD 2 -d 192.168.0.0/16 <http://192.168.0.0/16> -j REJECT
> iptables -I FORWARD 2 -d 172.16.0.0/12 <http://172.16.0.0/12> -j REJECT
> iptables -I FORWARD 2 -d 10.0.0.0/8 <http://10.0.0.0/8> -j REJECT
>
> Unless I have inserted the rules at the wrong spot, it doesn't look good. See below, please:
>
> # Generated by iptables-save v1.6.1 on Mon Oct 14 18:33:31 2019
> *mangle
> :PREROUTING ACCEPT [54716:20906174]
> :INPUT ACCEPT [26852:4628015]
> :FORWARD ACCEPT [27829:16271441]
> :OUTPUT ACCEPT [25477:18649644]
> :POSTROUTING ACCEPT [52098:34734180]
> -A FORWARD -s 10.10.10.0/24 <http://10.10.10.0/24> -o eth0 -p tcp -m policy --dir in --pol ipsec -m tcp --tcp-flags SYN,RST SYN -m tcpmss --mss 1361:1536 -j TCPMSS --set-mss 1360
> COMMIT
> # Completed on Mon Oct 14 18:33:31 2019
> # Generated by iptables-save v1.6.1 on Mon Oct 14 18:33:31 2019
> *nat
> :PREROUTING ACCEPT [1575:110530]
> :INPUT ACCEPT [28:8296]
> :OUTPUT ACCEPT [429:29655]
> :POSTROUTING ACCEPT [429:29655]
> -A POSTROUTING -s 10.10.10.0/24 <http://10.10.10.0/24> -o eth0 -m policy --dir out --pol ipsec -j ACCEPT
> -A POSTROUTING -s 10.10.10.0/24 <http://10.10.10.0/24> -o eth0 -j MASQUERADE
> COMMIT
> # Completed on Mon Oct 14 18:33:31 2019
> # Generated by iptables-save v1.6.1 on Mon Oct 14 18:33:31 2019
> *filter
> :INPUT DROP [1:40]
> :FORWARD DROP [0:0]
> :OUTPUT ACCEPT [102:15526]
> -A INPUT -i lo -j ACCEPT
> -A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
> -A INPUT -p tcp -m tcp --dport 443 -j ACCEPT
> -A INPUT -p tcp -m tcp --dport 2022 -j ACCEPT
> -A INPUT -p udp -m udp --dport 500 -j ACCEPT
> -A INPUT -p udp -m udp --dport 4500 -j ACCEPT
> -A FORWARD -s 10.10.10.0/24 <http://10.10.10.0/24> -d 10.10.10.0/24 <http://10.10.10.0/24> -j DROP
> -A FORWARD -d 10.0.0.0/8 <http://10.0.0.0/8> -j REJECT --reject-with icmp-port-unreachable
> -A FORWARD -d 172.16.0.0/12 <http://172.16.0.0/12> -j REJECT --reject-with icmp-port-unreachable
> -A FORWARD -d 192.168.0.0/16 <http://192.168.0.0/16> -j REJECT --reject-with icmp-port-unreachable
> -A FORWARD -m policy --dir in --pol ipsec -j ACCEPT
> -A FORWARD -m policy --dir out --pol ipsec -j ACCEPT
> COMMIT
>
> If this doesn't work I have to fallback to your initial solution:
>
> iptables -I FORWARD 2 -m conntrack --ctstate NEW -m hashlimit --hashlimit-name NETSCAN --hashlimit-mode srcip --hashlimit-srcmask 32 --hashlimit-upto 5/s -j ACCEPT
>
> With the following outcome:
>
> # Generated by iptables-save v1.6.1 on Mon Oct 14 18:40:26 2019
> *filter
> :INPUT DROP [192413:18329342]
> :FORWARD DROP [340475:90672719]
> :OUTPUT ACCEPT [425183776:485173348374]
> -A INPUT -i lo -j ACCEPT
> -A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
> -A INPUT -p tcp -m tcp --dport 443 -j ACCEPT
> -A INPUT -p tcp -m tcp --dport 2022 -j ACCEPT
> -A INPUT -p udp -m udp --dport 500 -j ACCEPT
> -A INPUT -p udp -m udp --dport 4500 -j ACCEPT
> -A FORWARD -s 10.10.0.0/17 <http://10.10.0.0/17> -d 10.10.0.0/17 <http://10.10.0.0/17> -j DROP
> -A FORWARD -m conntrack --ctstate NEW -m hashlimit --hashlimit-upto 5/sec --hashlimit-burst 5 --hashlimit-mode srcip --hashlimit-name NETSCAN -j ACCEPT
> -A FORWARD -m policy --dir in --pol ipsec -j ACCEPT
> -A FORWARD -m policy --dir out --pol ipsec -j ACCEPT
> COMMIT
> # Completed on Mon Oct 14 18:40:26 2019
> # Generated by iptables-save v1.6.1 on Mon Oct 14 18:40:26 2019
> *nat
> :PREROUTING ACCEPT [133256521:12349660945]
> :INPUT ACCEPT [805996:248685578]
> :OUTPUT ACCEPT [151185:15397949]
> :POSTROUTING ACCEPT [151185:15397949]
> -A POSTROUTING -s 10.10.0.0/17 <http://10.10.0.0/17> -o enp2s0 -m policy --dir out --pol ipsec -j ACCEPT
> -A POSTROUTING -s 10.10.0.0/17 <http://10.10.0.0/17> -o enp2s0 -j MASQUERADE
> COMMIT
> # Completed on Mon Oct 14 18:40:26 2019
> # Generated by iptables-save v1.6.1 on Mon Oct 14 18:40:26 2019
> *mangle
> :PREROUTING ACCEPT [47285409804:29854894928171]
> :INPUT ACCEPT [16114043471:4661974048771]
> :FORWARD ACCEPT [31166444886:25192112917092]
> :OUTPUT ACCEPT [20092152323:23622919704514]
> :POSTROUTING ACCEPT [51247881050:48812187889401]
> -A FORWARD -s 10.10.0.0/17 <http://10.10.0.0/17> -o enp2s0 -p tcp -m policy --dir in --pol ipsec -m tcp --tcp-flags SYN,RST SYN -m tcpmss --mss 1361:1536 -j TCPMSS --set-mss 1360
> COMMIT
> # Completed on Mon Oct 14 18:40:26 2019
>
> The latter doesn't stop the VPN, but I won't know it really prevents someone from running netscan until someone tries a new attempt again. :)
>
> What do you think?
>
> Many Thanks,
> Houman
>
>
> On Mon, 14 Oct 2019 at 17:05, Noel Kuntze <noel.kuntze at thermi.consulting> wrote:
>
>     Hello Houman,
>
>     Depends on what exactly you're doing on your server. It's not possible to give you a generalized answer.
>     You shouldn't script with iptables though. Use iptables-save and -restore (save prints out a serialised form of your loaded iptables rules, restore loads data in said form).
>
>     Kind regards
>
>     Noel
>
>     Am 14.10.19 um 14:30 schrieb Houman:
>     > Hello Noel,
>     >
>     > It's a bare-metal server that I'm renting (it's not a virtual server) so I assume that it should be in its own private subnet. I have tried to follow up with them, but their support doesn't communicate very well in English. All I could gather is the following:
>     >
>     > 1) Based on the ROOT SERVER SERVICE AGREEMENT, the scanning of foreign networks or foreign IP addresses is not permitted.
>     > 2) These RFC1918 networks are not reachable via my external interface (Then why is it a problem? I don't understand them)
>     >
>     > I did some further research. It seems it is better to do the REJECT rule only on the interface that is connected to the Internet. Otherwise, I could be blocking LAN or vpn peer-to-peer communications. 
>     >
>     > |export INET_IFACE=$(ip route get 8.8.8.8 | awk -- '{printf $5}')|
>     > |iptables -A FORWARD -o $INET_IFACE -d 10.0.0.0/8 <http://10.0.0.0/8> <http://10.0.0.0/8> -j REJECT iptables -A FORWARD -o $INET_IFACE -d 172.16.0.0/12 <http://172.16.0.0/12> <http://172.16.0.0/12> -j REJECT iptables -A FORWARD -o $INET_IFACE -d 192.168.0.0/16 <http://192.168.0.0/16> <http://192.168.0.0/16> -j REJECT|
>     > Do you agree with this? Or is it rather unnecessary for a StrongSwan server?
>     >
>     > Thanks,
>     > Houman
>     >
>     >
>     >
>     >
>     > On Mon, 14 Oct 2019 at 14:00, Noel Kuntze <noel.kuntze at thermi.consulting> wrote:
>     >
>     >     Hello Houman,
>     >
>     >     You can do that. I wonder though why that is a problem. Are they providing a private subnet on the link of your server?
>     >
>     >     Kind regards
>     >
>     >     Noel
>     >
>     >     Am 14.10.19 um 12:03 schrieb Houman:
>     >     > Hi Noel,
>     >     >
>     >     > That makes sense, thank you.
>     >     >
>     >     > I received a followup email from our server provider (about a new netscan attempt from one of our users today).
>     >     >
>     >     > """
>     >     > We would recommend that you set up a local firewall and block outgoing traffic to the following prefixes
>     >     > https://tools.ietf.org/html/rfc1918
>     >     > > 10.0.0.0/8 <http://10.0.0.0/8> <http://10.0.0.0/8> <http://10.0.0.0/8>
>     >     > > 172.16.0.0/12 <http://172.16.0.0/12> <http://172.16.0.0/12> <http://172.16.0.0/12>
>     >     > > 192.168.0.0/16 <http://192.168.0.0/16> <http://192.168.0.0/16> <http://192.168.0.0/16>
>     >     > Please block this range of RFC1918 on your server. 
>     >     > We would like to avoid further network abuse from your end.
>     >     > """
>     >     >
>     >     > Is this as simple as
>     >     >
>     >     > iptables -A FORWARD -d 10.0.0.0/8 <http://10.0.0.0/8> <http://10.0.0.0/8> <http://10.0.0.0/8> -j REJECT
>     >     > iptables -A FORWARD -d 172.16.0.0/12 <http://172.16.0.0/12> <http://172.16.0.0/12> <http://172.16.0.0/12> -j REJECT
>     >     > iptables -A FORWARD -d 192.168.0.0/16 <http://192.168.0.0/16> <http://192.168.0.0/16> <http://192.168.0.0/16> -j REJECT
>     >     >
>     >     > Or am I oversimplifying this?
>     >     >
>     >     > Many Thanks,
>     >     > Houman
>     >     >
>     >     >
>     >     > On Mon, 14 Oct 2019 at 13:02, Noel Kuntze <noel.kuntze at thermi.consulting> wrote:
>     >     >
>     >     >     Hello Houman,
>     >     >
>     >     >     Depends on if you have a whitelist or blacklist rule set.
>     >     >
>     >     >     With the ruleset you have provided in this email, you need to accept the stuff you want. So up to 5 new connections per second.
>     >     >
>     >     >     Kind regards
>     >     >
>     >     >     Noel
>     >     >
>     >     >     Am 14.10.19 um 10:40 schrieb Houman:
>     >     >     > Hi Noel,
>     >     >     >
>     >     >     > Actually based on my firewall config, I think I have to DROP it instead of ACCEPT if it's over the 5/sec limit?  Don't you agree?
>     >     >     >
>     >     >     > iptables -I FORWARD 2 -m conntrack --ctstate NEW -m hashlimit --hashlimit-name NETSCAN --hashlimit-mode srcip --hashlimit-srcmask 32 --hashlimit-above 5/s -j DROP
>     >     >     >
>     >     >     > So I replace *hashlimit-upto* with *hashlimit-above* following with a DROP.
>     >     >     >
>     >     >     > This is my current firewall settings based on your previous suggestion. If Iptables is clever enough to DROP the connection if hashlimit-upto is exceeded, it should work as well.
>     >     >     >
>     >     >     > # iptables-save
>     >     >     > *filter
>     >     >     > :INPUT DROP [6374:460035]
>     >     >     > :FORWARD DROP [7119:2071794]
>     >     >     > :OUTPUT ACCEPT [19665335:23255290771]
>     >     >     > -A INPUT -i lo -j ACCEPT
>     >     >     > -A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
>     >     >     > -A INPUT -p tcp -m tcp --dport 443 -j ACCEPT
>     >     >     > -A INPUT -p tcp -m tcp --dport 2022 -j ACCEPT
>     >     >     > -A INPUT -p udp -m udp --dport 500 -j ACCEPT
>     >     >     > -A INPUT -p udp -m udp --dport 4500 -j ACCEPT
>     >     >     > -A FORWARD -s 10.10.0.0/17 <http://10.10.0.0/17> <http://10.10.0.0/17> <http://10.10.0.0/17> <http://10.10.0.0/17> -d 10.10.0.0/17 <http://10.10.0.0/17> <http://10.10.0.0/17> <http://10.10.0.0/17> <http://10.10.0.0/17> -j DROP
>     >     >     > -A FORWARD -m conntrack --ctstate NEW -m hashlimit --hashlimit-upto 5/sec --hashlimit-burst 5 --hashlimit-mode srcip --hashlimit-name NETSCAN -j ACCEPT
>     >     >     > -A FORWARD -m policy --dir in --pol ipsec -j ACCEPT
>     >     >     > -A FORWARD -m policy --dir out --pol ipsec -j ACCEPT
>     >     >     > COMMIT
>     >     >     > # Completed on Mon Oct 14 08:30:14 2019
>     >     >     > # Generated by iptables-save v1.6.1 on Mon Oct 14 08:30:14 2019
>     >     >     > *nat
>     >     >     > :PREROUTING ACCEPT [222978690:20761159044]
>     >     >     > :INPUT ACCEPT [1143238:398065963]
>     >     >     > :OUTPUT ACCEPT [245876:24207759]
>     >     >     > :POSTROUTING ACCEPT [245876:24207759]
>     >     >     > -A POSTROUTING -s 10.10.0.0/17 <http://10.10.0.0/17> <http://10.10.0.0/17> <http://10.10.0.0/17> <http://10.10.0.0/17> -o enp2s0 -m policy --dir out --pol ipsec -j ACCEPT
>     >     >     > -A POSTROUTING -s 10.10.0.0/17 <http://10.10.0.0/17> <http://10.10.0.0/17> <http://10.10.0.0/17> <http://10.10.0.0/17> -o enp2s0 -j MASQUERADE
>     >     >     > COMMIT
>     >     >     > # Completed on Mon Oct 14 08:30:14 2019
>     >     >     > # Generated by iptables-save v1.6.1 on Mon Oct 14 08:30:14 2019
>     >     >     > *mangle
>     >     >     > :PREROUTING ACCEPT [76920955633:50815277695359]
>     >     >     > :INPUT ACCEPT [27612054762:8305407205459]
>     >     >     > :FORWARD ACCEPT [49298861266:42508240159831]
>     >     >     > :OUTPUT ACCEPT [34323442858:39692165780388]
>     >     >     > :POSTROUTING ACCEPT [83603096494:82195502934979]
>     >     >     > -A FORWARD -s 10.10.0.0/17 <http://10.10.0.0/17> <http://10.10.0.0/17> <http://10.10.0.0/17> <http://10.10.0.0/17> -o enp2s0 -p tcp -m policy --dir in --pol ipsec -m tcp --tcp-flags SYN,RST SYN -m tcpmss --mss 1361:1536 -j TCPMSS --set-mss 1360
>     >     >     > COMMIT
>     >     >     >
>     >     >     > On Mon, 14 Oct 2019 at 11:14, Houman <houmie at gmail.com <mailto:houmie at gmail.com> <mailto:houmie at gmail.com <mailto:houmie at gmail.com>> <mailto:houmie at gmail.com <mailto:houmie at gmail.com> <mailto:houmie at gmail.com <mailto:houmie at gmail.com>>> <mailto:houmie at gmail.com <mailto:houmie at gmail.com> <mailto:houmie at gmail.com <mailto:houmie at gmail.com>> <mailto:houmie at gmail.com <mailto:houmie at gmail.com> <mailto:houmie at gmail.com <mailto:houmie at gmail.com>>>>> wrote:
>     >     >     >
>     >     >     >     Hello Noel,
>     >     >     >
>     >     >     >     Thanks for your solution, I just tried it:
>     >     >     >
>     >     >     >     iptables -I FORWARD 2 -m conntrack --ctstate NEW -m hashlimit --hashlimit-mode srcip --hashlimit-srcmask 32 --hashlimit-upto 5/s -j ACCEPT
>     >     >     >
>     >     >     >     But I got this error message:
>     >     >     >
>     >     >     >     iptables v1.6.1: hashlimit: option "--hashlimit-name" must be specified
>     >     >     >
>     >     >     >     I googled and added the missing name like this:
>     >     >     >
>     >     >     >     iptables -I FORWARD 2 -m conntrack --ctstate NEW -m hashlimit --hashlimit-name NETSCAN --hashlimit-mode srcip --hashlimit-srcmask 32 --hashlimit-upto 5/s -j ACCEPT
>     >     >     >
>     >     >     >     Do you agree with this approach to prevent VPN users from running Netscans?
>     >     >     >
>     >     >     >     Many Thanks,
>     >     >     >     Houman
>     >     >     >
>     >     >     >
>     >     >     >     On Wed, 31 Jul 2019 at 14:51, Noel Kuntze <noel.kuntze at thermi.consulting> wrote:
>     >     >     >
>     >     >     >         Hello Houman,
>     >     >     >
>     >     >     >         A "netscan" attack isn't actually anything worthy of an abuse email.
>     >     >     >         It's not part of a benign usage pattern of a VPN service, but it itself isn't illegal or anything.
>     >     >     >         You can only slow down such scans by rate limiting the number of new connections using the hashlimit match module, for example.
>     >     >     >
>     >     >     >         E.g. -A FORWARD -m conntrack --ctstate NEW -m hashlimit --hashlimit-mode srcip --hashlimit-srcmask 32 --hashlimit-upto 5/s -j ACCEPT
>     >     >     >
>     >     >     >         Kind regards
>     >     >     >
>     >     >     >         Noel
>     >     >     >
>     >     >     >         Am 30.07.19 um 16:39 schrieb Houman:
>     >     >     >         > Sorry I mistyped. I meant  Netscan.
>     >     >     >         >
>     >     >     >         > The abuse message was saying: *NetscanOutLevel: Netscan detected from xx.xx.xx.xx*
>     >     >     >         >
>     >     >     >         > This is possible though, that VPN users run a netscan and scan the ports. Am I correct?
>     >     >     >         >
>     >     >     >         > Thanks,
>     >     >     >         >
>     >     >     >         > On Tue, 30 Jul 2019 at 15:30, Thor Simon <Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com>> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com>>> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com>> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com>>>> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com>> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com>>> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com>>
>     <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com> <mailto:Thor.Simon at twosigma.com <mailto:Thor.Simon at twosigma.com>>>>>> wrote:
>     >     >     >         >
>     >     >     >         >     I don't think netstat does what you think it does.  It is a _local_ tool.  Perhaps the "abuse notification" you received is a phishing attack?
>     >     >     >         >
>     >     >     >         >     Hae a look at the manual page:
>     >     >     >         >
>     >     >     >         >     http://manpages.ubuntu.com/manpages/trusty/man8/netstat.8.html
>     >     >     >         >
>     >     >     >         >     ________________________________
>     >     >     >         >     From: Houman <houmie at gmail.com <mailto:houmie at gmail.com> <mailto:houmie at gmail.com <mailto:houmie at gmail.com>> <mailto:houmie at gmail.com <mailto:houmie at gmail.com> <mailto:houmie at gmail.com <mailto:houmie at gmail.com>>> <mailto:houmie at gmail.com <mailto:houmie at gmail.com> <mailto:houmie at gmail.com <mailto:houmie at gmail.com>> <mailto:houmie at gmail.com <mailto:houmie at gmail.com> <mailto:houmie at gmail.com <mailto:houmie at gmail.com>>>> <mailto:houmie at gmail.com <mailto:houmie at gmail.com> <mailto:houmie at gmail.com <mailto:houmie at gmail.com>> <mailto:houmie at gmail.com <mailto:houmie at gmail.com> <mailto:houmie at gmail.com <mailto:houmie at gmail.com>>> <mailto:houmie at gmail.com <mailto:houmie at gmail.com> <mailto:houmie at gmail.com <mailto:houmie at gmail.com>> <mailto:houmie at gmail.com <mailto:houmie at gmail.com> <mailto:houmie at gmail.com <mailto:houmie at gmail.com>>>>>>
>     >     >     >         >     Sent: Jul 30, 2019 10:18 AM
>     >     >     >         >     To: users at lists.strongswan.org <mailto:users at lists.strongswan.org> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org>> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org>>> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org>> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org>>>> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org>> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org>>> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org>
>     <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org>> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org> <mailto:users at lists.strongswan.org <mailto:users at lists.strongswan.org>>>>>
>     >     >     >         >     Subject: [strongSwan] How to block Netstat attacks from VPN users?
>     >     >     >         >
>     >     >     >         >     Hello,
>     >     >     >         >
>     >     >     >         >     I had an interesting abuse notification that someone has run a netstat through our VPN.
>     >     >     >         >
>     >     >     >         >     > time                protocol src_ip src_port          dest_ip dest_port
>     >     >     >         >     > ---------------------------------------------------------------------------
>     >     >     >         >     > Tue Jul 30 13:38:01 2019 UDP 136.243.xxx.xxx 21346 =>    172.20.10.17 21346
>     >     >     >         >     > Tue Jul 30 13:38:01 2019 UDP 136.243.xxx.xxx 21346 =>    172.20.10.19 21346
>     >     >     >         >
>     >     >     >         >     I was wondering if there is a good way to block all VPN users from running hacker tools such as netstat (port scanning) altogether.  Is there a reliable way to do that with iptables?
>     >     >     >         >
>     >     >     >         >     I came across this snippet that should block port scans, but I'm not sure if that would block a VPN user after all since the VPN traffic is masqueraded.
>     >     >     >         >
>     >     >     >         >     iptables -A port-scan -p tcp --tcp-flags SYN,ACK,FIN,RST RST -m limit --limit 1/s -j RETURN
>     >     >     >         >     iptables -A port-scan -j DROP --log-level 6
>     >     >     >         >     iptables -A specific-rule-set -p tcp --syn -j syn-flood
>     >     >     >         >     iptables -A specific-rule-set -p tcp --tcp-flags SYN,ACK,FIN,RST RST -j port-scan
>     >     >     >         >
>     >     >     >         >     Any suggestions, please?
>     >     >     >         >     Many Thanks,
>     >     >     >         >     Houman
>     >     >     >         >
>     >     >     >         >
>     >     >     >         >
>     >     >     >
>     >     >     >         --
>     >     >     >         Noel Kuntze
>     >     >     >         IT security consultant
>     >     >     >
>     >     >     >         GPG Key ID: 0x0739AD6C
>     >     >     >         Fingerprint: 3524 93BE B5F7 8E63 1372 AF2D F54E E40B 0739 AD6C
>     >     >     >
>     >     >     >
>     >     >
>     >     >     --
>     >     >     Noel Kuntze
>     >     >     IT security consultant
>     >     >
>     >     >     GPG Key ID: 0x0739AD6C
>     >     >     Fingerprint: 3524 93BE B5F7 8E63 1372 AF2D F54E E40B 0739 AD6C
>     >     >
>     >     >
>     >
>     >     --
>     >     Noel Kuntze
>     >     IT security consultant
>     >
>     >     GPG Key ID: 0x0739AD6C
>     >     Fingerprint: 3524 93BE B5F7 8E63 1372 AF2D F54E E40B 0739 AD6C
>     >
>     >
>
>     -- 
>     Noel Kuntze
>     IT security consultant
>
>     GPG Key ID: 0x0739AD6C
>     Fingerprint: 3524 93BE B5F7 8E63 1372 AF2D F54E E40B 0739 AD6C
>

-- 
Noel Kuntze
IT security consultant

GPG Key ID: 0x0739AD6C
Fingerprint: 3524 93BE B5F7 8E63 1372 AF2D F54E E40B 0739 AD6C

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: OpenPGP digital signature
URL: <http://lists.strongswan.org/pipermail/users/attachments/20191014/b8ded86d/attachment-0001.sig>


More information about the Users mailing list