Security :: Firewall Deny Traffic Inbound Destination Port 53372 & 53375?

May 5, 2010

I have a question, on my firewall at work I am seeing a constant flow of denies from many different source IP addresses, of tcp/udp destination port 53372 & 53375.What in the world is that, and why these two ports over and over

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Security :: Drop Inbound Traffic To Port 80 (http) From Source Ports Less Than 1024?

Feb 1, 2011

I'm simply trying to make a little restriction on www packets under two rules:

1. Allow inbound/outbound www packets (works!)

2. DROP inbound traffic to port 80 from source ports less than 1024. (DOES NOT WORK!)

Now, technically, when i use hping to test my rules, hping3 -S -p80 -s 1023 I should NOT receive any packets. However, i still receive packets, which means my rule that says less than 1024 does not work. (see below)

And this is my iptables rules in shell-script so far:



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Security :: Firewall, Can't Deny Ips After Allowing Local Subnet?

Feb 23, 2010

If I allow, my server's IP is:

If I allow, and block can't access the server

But if I allow, and block can still access the server!!

Does anyone know why that is?

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Security :: Deny Host When Changing SSH Port 22

Oct 30, 2010

I have an Asterisk on an externally hosted vServer with Lenny. In order to further protect the SSH access I intended to change the Port number 22 to something like 55555. For this I changed the /etc/ssh/sshd_config file and restarted ssh. This caused unfortunately the following problems:

(1) The first login works but DenyHost writes now the IP in its list so that the second login with the same IP is blocked.

(2) With RESET_ON_SUCCESS = yes several logins were possible with the same IP, but later it also was blocked for some still unknown reasons.

(3) Files can be uploaded for being edited, but they can't always be saved. When they can't be saved the next login with this IP is blocked. It thus looks like the blocking can occur while being connected. When the files can't be saved it is however still possible to copy files from the computer to the vServer.

I add below the entries in the auth.log from a logout and a login. It shows further how suddenly the attempts to save files were blocked. After this session the IP used for it was blocked. I don't know where the message "Unable to open env file: /etc/default/locale" comes from. If I remember right I had these messages already before. I don't know how much that is really important.


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Security :: Iptables: Verify Traffic On Port To Check If It Is Legitimate For That Port?

Apr 18, 2011

Is there any way to verify if packets being trafficked over a certain port are valid for the service you want to use this port for?

One obvious example that probably clarifies my question:
When I open port 443 (outgoing or incoming) for https/ssl traffic, I don't want this port to be used for say openvpn traffic.
Thus: when someone wants to surf to a website with https, it should be ok but if someone wants to connect to his home openvpn server over that same port, it should be blocked.

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Security :: Is A Firewall Needed If Get All Traffic Through A Router

Aug 8, 2010

I get all my traffic from my router, as this computer seldom moves. So is there a use for a firewall?I am not sure, because when I scan my IP address with nmap, no matter what the changes I make in the firewall, it is always the same scan...cannot fingerprint OS...and all closed ports.The all closed ports thing only changes when i torrent, then i get a wide open port.

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Ubuntu Security :: Firewall: Completely Prevent Any Traffic From Network?

Jan 4, 2010

I have Ubuntu 8.04 as virtual host. On this host I have installed VirtualBox virtualization software. I have installed Windows XP as virtual machine and installed HTTP server.I would like temporally disable all network connections to host and virtual machine.So on Ubuntu host I have set firewall settings:

sudo iptables -F (to flush - delete all firewall settings)
sudo iptables -P INPUT DROP (to disable all input traffic)


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General :: How To Enable Inbound Traffic

Jul 20, 2010

1. It is definitely my system and not the router. I had been accepting these connections just fine on my Fedora 6 system, but upgraded to FC11 and haven't been able to get these inbound connections working. I still have the drive with the FC6 system and whenever I put the old drive in the system, the connections work fine. So, the hardware, wiring, etc is identical between the FC6 and FC11 systems.

2. The system's firewall is disabled. iptables, and ip6tables are turned off both at startup (e.g., chkconfig iptables off) and using "service iptables stop". (Note--my router also works as a firewall)

3. sshd and httpd are both on and listening on all interfaces. "nmap -P0 -p 22,80" shows both ports open, as does But when I use the same command looping through the external IP, the ports are filtered:

Host is up.
22/tcp filtered ssh
80/tcp filtered http

4. hosts.deny is empty.

5. The messages and secure logs do not show anything in response to the nmap scans.

Again, I'd have sworn this was my router, except that it cleanly allows the traffic when I swap the drives in my system.

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Security :: Updates: Specify Source Port For Traffic?

Dec 14, 2010

I've a server, and I want to drop all the traffic going out with other source port than 80 (apache) and 22(ssh). The reason is I want to prevent my machine sending packets I don't know (i.e. my server scanning networks or making DDOS attacks without my knowledge). The problem are the updates. If I do what I've said, the updates will not work. I want to allow updates, so I need to let DNS traffic (port 53) and the traffic of the updates to go out.

The problem is the source port. This traffic uses a dynamic port (I think like HTTP). Is there any way to specify a source port to do this? If a have a static port to do this, I would drop all the traffic going out with other port than 22,53,80 and this port.

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Software :: Using Squid/Iptables To Redirect Inbound Web Traffic To Url/IP

Jan 13, 2010

We host a web server in which we are hoping to implement some form of traffic redirection based on source IP address, and I am wondering whether the squid proxy built on iptables would be capable of managing this task? Essentially we are trying to redirect traffic from specific set of source IP ranges to a "Your IP has been restricted" type of page at a different IP/FQDN.

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Security :: Closing Port 23 With The Mandriva Firewall?

Jul 17, 2010

I just installed Mandriva 2010 and set up the interactive firewall via the MLCC. I set it up not to allow any services to connect (didn't check any boxes). However, when I check my system using a port scanner (shields up at it says that port 23 is open. Does anyone know why this would be and how I can close it When I look at the daemons running I notice that iptables and ip6tables are 'stopped' although shorewall is running - is this correct? I (perhaps wrongly) thought that iptables needed to be running in order for the firewall to work properly.

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CentOS 5 Networking :: Configure Firewall - Allow And Forward All Traffic On Eth0 And Block All Traffic On Eth1 Except Ssh Ping

Sep 29, 2010

I need to set up my centOS computer as a firewall in my home network. Ive got 2 interfaces, eth0 and eth1. I want to allow and forward all traffic on eth0 and block all traffic on eth1 except ssh, ping(icmp) and DNS. How do I do this? Ive tried some editing in /etc/sysconfig/iptables but no luck.

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Ubuntu Security :: Firewall Can Install Only Let Certain MAC Addresses Through On Certain Port?

Jul 25, 2010

Is there a firewall I can install that will only let certain MAC addresses through on a certain port?

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Ubuntu Security :: Cannot Connect To Port Number / When Firewall Is Enabled

Sep 5, 2010

i am using 9.10 karmic. Firewall is enabled. added ports with ufw allow [portnumber], and i still cannot connect to a port number. iv tryed ufw allow ssh/tcp but that does not work. the ports work when i disable the firewall and i dont want to do that.

ufw is available in all new installations of Ubuntu since 8.04 LTS, but is disabled by default. The standard Ubuntu installation has a no open service ports policy, so enabling the firewall by default doesn't gain any extra security in the default installation, but could provide confusion for people new to Ubuntu when new software that is installed does not work because of restrictive firewall rules. As a result, when first adding ufw to Ubuntu it was decided that users must 'opt-in' to using the firewall. In Ubuntu 9.04 and later, you can enable ufw during installation using preseeding. See /usr/share/doc/ufw/README.Debian for details.

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Server :: Squid3 Deny All Traffic (Ignoring ACL)

Feb 18, 2010

I have a squid3 on a debian lenny box but cannot get access to any site.

If i remove the http_access deny all works, but i just want those ip to get access to squid

My squid.conf

intranet:/etc/squid3# cat squid.conf
acl manager proto cache_object
acl localhost src
acl to_localhost dst
#acl all src


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Server :: Sendmail For Inbound Mail And Redirecting Them Internally To Other Port?

Mar 22, 2011

I have configured a sendmail MTA for incoming mails in a network and by using IPtables i have redirected the traffic internally to other port where one more SMTP by a application is running.Iptables rule:

iptables -A INPUT -i eth0 -p tcp --dport 25 -j ACCEPT
iptables -A PREROUTING -t nat -i eth0 -p tcp --dport 25 -j REDIRECT --to-port 25000

My sendmail config is as below.
define(`SMART_HOST', `')dnl
dnl # define(`RELAY_MAILER',`esmtp')dnl


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Ubuntu :: Firewall Of Destination Avoid Answering To Pings / Get Name's IP Without Using It?

Feb 15, 2011

I need to check the output of a name resolution, but I configured the firewall of the destination to avoid answering to pings.
Is there any other way to get a name's IP without using ping? (I mean something like $resolv

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General :: Define Both Source/Destination AND Direction When Building Firewall?

May 30, 2011

why do we have to define both Source/Destination AND Direction when building firewall.Isn't direction= source->destination? what would happen if source and destination were swapped?

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Ubuntu Security :: 10.10 - Inbound Connections And Firestarter

Apr 6, 2011

I am running Ubuntu 10.10 I have an question about the firewall Firestarter, when checking the firewall it told me there are 9 serious incoming connections what must I do with this info. Inbound is normally blocked as standard i have also see that someone with port 1234 and 12345 have trying to attempt mine system but failed all trojan ports are fully blocked.

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Security :: Adjust Iptables To Only Inbound Syn Connections

Apr 7, 2011

I'm trying to adjust the firewall to only inbound syn connections.

To Allow all home subnets access to port 53 both tcp/udp but deny the rest.

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General :: How To Configure Juniper SSG140 Deny Port 80&443 Except Squid Proxy

Dec 22, 2010

I have just installed Squid proxy. i also use WPAD to deploy policies for all client. Both works well together. Now i want to configure firewall Juniper SSG140 will be deny all request from client to access internet and redirect to Squid. I mean deny HTTP & HTTPS except Squid (port 3128), even i want to all access to internet have to through Squid proxy. I don't expert about the firewall Juniper. May i know step by step configure it.


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Server :: If Forward A Port In Iptables, Does The Port Have To Be Open On The Firewall

Aug 5, 2009

If I forward port 80 to port 3128 for squid with an iptable rule, does port 3128 have to be open on the firewall or is this all routed behind the firewall?

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Ubuntu Networking :: Using Iptables To Change A Destination Port But Keep The Ip The Same?

Mar 23, 2010

I am playing around with transparent proxies, The current way I am doing things is the program makes a request to a computer on port 80, I use

iptables -t nat -A OUTPUT -p tcp --destination-port 80 -j REDIRECT --to-port 1234 to redirect to my proxy that I am playing with. the proxy will send out a request to port 81 (as all outbound port 80 are being fed back in to the proxy) so I want to do something like

iptables -t nat -A OUTPUT -p tcp --destination-port 81 -j DNAT --to-destination xxxx:80 The problem lies with the xxxx part. How do I change the destination port without changing changing the destination ip? Or am I doing this setup completely wrong,

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Programming :: Raw UDP Socket And ICMP Destination (Port) Unreachable?

Oct 26, 2009

I'm using a single raw socket to read UDP packets from local test network with 1024 ports. Each UDP src and dest port is unique and I need access to IP and UDP header fields. I can stream and process data (in and out) at 100 mbps in linux-rt kernel with very low jitter < 250 usec, 10 usec nominal.

I'd like to prevent kernel from issuing ICMP port unreachable errors back to the sending host, however, I don't want to create 1024 vanilla UDP sockets and bind to each one because of resource constraints. Currently, I'm using iptables to drop the outbound port unreachable messages. Does anyone know of a way (programmatic using C code) to prevent the ICMP unreachable traffic? Perhaps an IOCTL or socket option? I also tried changing /proc/sys/net/ipv4/icmp_ratelimit but that seemed to have no effect. By default the ratemask is set for dest unreachables and a variety of ratelimit values did not change any behavior that I could see.

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Fedora Security :: Iptables To Deny All Except Localhost?

May 15, 2011

i was hoping that someone in here could possibly help me out with my iptables rule set. First here is what i would like iptables to do, i want iptables to deny all packets or traffic from the outside coming in and for output allow the things i need like web and irc etc... Also, i would like iptables to deny access to all services like sendmail and ssh except i would like localhost to have access to everything. What i mean by localhost is that when i run my iptables script it loads fine except when i try ssh from localhost i get this output:ssh -l user localhostssh_exchange_identification: Connection closed by remote hostI know what most of you are thinking, why do i need to ssh into localhost from localhost just open another terminal, well i am getting myself familiar with iptables i want all services logged and blocked but not from localhost. I cant seem to figure out this problem and i have tried several different things. Here is my iptables script, I am hoping that someone out there can tell me what i am doing wrong...

iptables -v -F;
iptables -v -A INPUT -i lo -j ACCEPT;


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Security :: Deny Root Access To A Given File

Dec 7, 2010

I would like to know if it is possible to deny the access to a file for root? Would ACL's be a possibility? I have "googled" around but haven't found anything interesting (except SELinux). I should secure a password file to an important database.

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Security :: Configure Deny.hosts For Opensuse 11.1?

Sep 7, 2010

I just downloaded the DenyHosts2.6python2.5.rpm for deny.hosts from sourceforge and would like to set it up. I normally use fish://, smb:// and ftp:// on the boxes on my lan. I already have files called hosts.allow and hosts.deny in the /etc folder. Will the rpm configure hosts.deny when first run?

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General :: Is There Interactive Firewall For Outbound Traffic On Ubuntu?

Aug 24, 2010

I wish to prevent some programs from "phoning home", and to allow other programs to access only specific web servers.Is there any way to interactively allow or decline outbound communication from individual programs on Ubuntu?

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Networking :: Capture And Log All LAN Traffic - No Access To Router Or Firewall

Jun 10, 2009

I am looking for a solution for our LAN traffic monitoring and would like to use some opensource linux application. I have a linux box with two NIC cards and what I thought is the following: Our setup is as follows. Internet comes in through the router and into the firewall. From the firewall it goes into our switch and distributed among the workstations.
I have no access to the router or the firewall as they are centrally configured. I would like to place a device into the loop through which I could monitor the LAN traffic.

Can I put a linux box between the firewall and the switch and have all packets going through registered and logged? I have a proxy server (non transparent) and that captures some but not all. I would like to get all packets registered without interfering with the LAN etc.

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Networking :: Preventing Internal Network Traffic With Firewall

Jul 3, 2010

Does anyone know if it is possible to filter/block network traffic between internal hosts on a lan?

Eg. : Linux firewall/router ( - LAN Default G/W - all internal > external traffic gets filtered.

How would you filter tcp/ICMP/UDP traffic from internal host a ( ) to host b (

All the internal hosts have the linux f/w as the default gateway, and are all on the same /24 subnet.

I would like to know if I can filter traffic between internal hosts.

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