Concerned with software or hardware firewalls

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Security concerns allowing internet connected server to write on network server

I don't know much about network engineering since I just started becoming a programmer. The situation is, that my company has a web-interface hosted on one of our servers that is connected to the ...
5
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3answers
312 views

What are the security implications of allowing unlimited size cookies?

Our application firewall blocks requests if it detects a cookie is present with a value greater than 1024 characters in size. Are there any exploits involving large cookies? i.e. How much more ...
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2answers
3k views

Firewall Configuration Audits

I'm looking to perform policy audits against firewall configurations and/or rulesets. This should be performed independently of any configuration management systems, ideally by operating off the ...
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1answer
1k views

I'm having a DDoS attack, my hosting company is stupid, and I need to know what is hapening

So ok, right now my windows 2003 dedicated server is under attack by some guy who's flooding UDP packets (~90.000 packets/sec) on my 100Mbps server for the last 8 hours. I'm on a shared port, so I'm ...
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2answers
5k views

Docker port forwarding exposure

I try docker with a simple webapp : docker run -d -v $(pwd):/app -p 8080:80 image_name I have docker listen on 8080: tcp6 0 0 :::8080 :::* LISTEN ...
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2answers
504 views

Security risks of leaving open a VPN connection

We have older firewalls that don't allow for scheduling up/down times of VPN connections, and we're working with a client that will need to connect to it at different times each day. What are the ...
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1answer
7k views

Is it safe to disable connection tracking in iptables?

While reading about NOTRACK target of raw table in iptables, I encountered an article suggesting that for certain traffic you could (or even should) disable connection tracking. The two examples were: ...
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2answers
354 views

Port forwarding with 0.0.0.0, any threat?

I set up on our company's firewall (fortigate100d) a port forwarding to one of our Internal services. As we don't have a static public IP I used 0.0.0.0 as an external IP so the remote users can ...
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1answer
1k views

Why ESTABLISHED,RELATED for INPUT only?

In many places and tutorials I see people add this line to their iptables: -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT And they do it only and only for "INPUT". What about OUTPUT and ...
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2answers
58 views

How does a firewall software intercept network communication?

I have a basic idea of what a software-based packet filter does, and I'm not sure if it's entirely accurate. Basically, a packet filter is a loadable kernel module that is inserted into the network ...
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2answers
373 views

Is this a DNS attack?

The following graph shows the UDP DNS queries/sec (blue) and DNS responses/sec (red) of traffic passing a router over the preiod of 4 days. DNS query is a DNS packet with query/response flag set to 0 ...
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2answers
852 views

What are the risks associated with relying on IPSec IP Filtering?

When using Windows IPSec for IP filtering whenever a filter is added you need to have a "mirror" rule (by checking the "Mirrored. Match packets..." tickbox). Because IPSec Filtering is not stateful, ...
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2answers
4k views

How should an outgoing connection white-list be created?

I see my previous question was closed as duplicate of Why block outgoing network traffic with a firewall?. The answers that everyone agree with mention the value of blocking outgoing connections (to ...
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4answers
1k views

What problems if any are caused by opening a port in the firewall that no program listens on?

I have a port forwarded and open in the firewall that I sometimes use to play games with friends over the internet. The game server doesn't run 24/7, only when I'm actually playing is something ...
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3answers
19k views

Best practice to block Dropbox usage

We have users sync their data at company with their home computer. What's the best way to block it? Block *.dropbox.com Find out all dropbox IPs and block IPs. For windows users, deploy GPO to ...
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5answers
413 views

Why wasn't the flame malware flagged by firewalls?

Why didn't any firewalls catch the flame malware siphoning out all of that data? I thought there was firewall software that looks for "suspicious" activity?
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8answers
58k views

How to block some websites in a small office?

I had a wireless connection in my office with one laptop. Now I bought two more laptops for my employees, and I give them Internet access. I want to block a few websites. My current connection is ...
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3answers
13k views

How to create ssh tunnel using netcat?

I want to create reverse connection between two machines, but these is a firewall in the middle preventing all connections, except ssh. I want to create ssh tunnel using netcat, could you please tell ...
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2answers
568 views

What is the background of the Reference Counter Overflow in Microsoft TCP/IP (MS11-083)?

How unique is this bug? Is there a more sophisticated and well-studied attempt behind? Is it accidence? The article below says "continouos stream to UDP". What stream? Just an hour stream of zeros? ...
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4answers
225 views

Can you use two hardware firewalls?

There is a rule that says "don't use/install more than one firewalls on one computer " (software firewalls to be exact) which means if you have a network and it has five computers you can only ...
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3answers
4k views

How do I configure nmap to verify my firewall is performing stateful packet inspection?

As part of a compliance audit, I need to run a routine scan that verifies that our firewalls are performing stateful packet inspection on incoming packets. I have a dedicated server outside our ...
4
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1answer
202 views

Is it possible to detect DPI (Deep Packet Inspection)?

If one suspects one's packets are subject to DPI, how can it be detected?
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4answers
7k views

HTTPS firewall rule

Setting up Firewall rule for HTTPS websites on basic stateless packet filter firewall This seems like a stupid question, but how do I set up a firewall rule to allow HTTPS on a basic packet filter ...
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3answers
376 views

The safest way to circumventing Iran's Internet censorship

We usually buy services like VPN, SOCKS, Kerio [Kerio Connect?]... to circumvent Iran's Internet censorship policy. Recently, one of the shops started selling [one of] Kerio's products, for which I do ...
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3answers
4k views

Which of these ports are safe to leave open, which are not?

I just ran nMap against my IP address and got the following result: PORT STATE SERVICE 21/tcp open ftp 22/tcp open ssh 23/tcp open telnet 80/tcp open http 443/tcp open https ...
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3answers
661 views

Servers: Why a separate device for a firewall, aside from reduction in IP spoofing or increase in performance

Why should the firewall be outside the server, excepting these two items Take the performance impact of noise off of the server. Add a physical layer between devices so they can be on separate ...
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2answers
86 views

Network UTM firewalls, are they really worth it?

I am currently looking at boosting the network security in my organization. (Currently we just use really basic small business network firewalls we primarily bought for IPSec VPNs). However, from ...
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2answers
122 views

Blacklisting IP addresses — when should we take action?

I am responsible for securing an AWS environment and am noticing various recon attacks against the environment. We have the option of blocking the IP addresses in our firewall, but the environment is ...
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2answers
387 views

If nmap reports a port is open, does that ALSO mean a service is listening on the port?

I have a Thompson TG585v7 router/firewall whose firewall is configured to FORWARD several ports to a computer X54 within the LAN. These ports are in the range 1024 through to 2500 That X54 ...
4
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1answer
477 views

How did my homepage get changed in IE?

I have rarely used IE in the past. I just use it to test how a website looks. Today all of a sudden when I went on to open IE, it opened with a homepage that wasn't set by me. It was an address of a ...
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3answers
11k views

How do you properly setup Tor on Windows 7?

How do you properly setup Tor on a Windows 7 box to guarantee that ALL connections will run through Tor?
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1answer
7k views

Fail2Ban does not ban failed root login attempt

I have a small server which only open ports are ssh, http and https. I have fail2ban installed and set up so that after 3 failed attempts someone gets blocked for 10 minutes (thats the dafault I ...
4
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2answers
617 views

Firewall design for big enterprise business

I am wondering if there is any best practice firewalling rules that should be put in effect in most modern networks. For example should the network atleast have the following firewall zones? Client ...
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2answers
4k views

What's the difference between an application-level and circuit-level gateway?

From Wikipedia, I understand that circuit level gateways look at TCP handshakes to filter illegitimate traffic and that application level gateways somehow filter application specific traffic. But I ...
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1answer
403 views

Exploited by newbie3viLc063s

My debian server got exploited by some scriptiekiddie who used Newbie3viLc063 http://pastebin.com/jma8JRG1 . Scriptkiddie uploaded logo_php.png to my server (My permissions sucked :s) and he did run ...
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3answers
11k views

Is it really better to use port 80 or 443 for outgoing traffic in order to bypass user firewall?

I recently created a reverse connection shell in C#. I tested it with some computers and I noticed that some computers connected back correctly and I established connection with them but another ...
4
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1answer
344 views

Placing a firewall—without creating a new subnetwork

I have a couple of networks that have multiple IP addresses, and where I have absolutely no choice as to the equipment used for the network's edge router (the device that connects both to the LAN and ...
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2answers
62 views

monitor port scan on the same segment

if theres a port scan on the same segment and it does not reach the firewall at all, it is not detectable by anything. is there any solution to that ? maybe using the windows fw on ach workstation to ...
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2k views

what is a good public available iptables script for ddos mitigation?

what is a good public available iptables script for ddos mitigation?
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2answers
2k views

Cisco ASA Security Contexts: Any Real World Installs?

We are looking at deploying a Cisco ASA 5520-I am looking at the security contexts feature, and was wondering if anyone has deployed their ASA in this way, and how it is working out for them. Have ...
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2answers
347 views

What criteria do you use for evaluating Client-Side / Endpoint security products?

What features are important to you in client-side AV and Firewall products? Who benefits from these features? Managment, the end user, helpdesk. Are there features that are being 'sold' by the ...
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1answer
152 views

Block this DDoS attack

since more than a week my dedicated server (located at ovh.com) has been under TCP SYN (I think) attack, ovh don't care about it but this attack is killing my server with a high CPU load (permanent ...
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2answers
77 views

Should I block outbound TCP RST (on closed ports)?

I have a range of inbound TCP ports open on the firewall, but usually closed on the host machine. I see a handful of unknown connection attempts each day, for which the server returns TCP RST. I ...
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2answers
182 views

Firewall egress filtering by domain

In our production environment, we are connecting to a few core external service providers though their APIs, and are required to have all other services blocked (PCI DSS). We currently have a ...
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3answers
2k views

Effectively limiting outgoing firewall traffic to frequently-changing IPs

PCI DSS 1.2.1 states: Restrict inbound and outbound traffic to that which is necessary for the cardholder data environment. Verify that all other inbound and outbound traffic is ...
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1answer
1k views

Firewall rules to block unwanted protocols on given ports

Does somebody has an idea, that what kind of iptables/pf rule must i use to achieve this?: i only want to allow these connections [on the output chain]: on port 53 output only allow udp - dns on ...
4
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2answers
108 views

When should I drop a packet with ICMP type 3, code 9 or 10, TCP RST, or TCP ACK?

This answer says there are a few ways of dealing with a blocked packet at a firewall: At each of these levels a 1st IP packet (and any other protocol packet as an ESP or AH packet) might receive ...
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1answer
599 views

Firewalk through a Firewall on our subnet

Having trouble firewalking. I am trying to determine all the open ports on my firewall/gateway. Here is my lab network diagram: (Skip to the bottom of the following explanation for a direct list of ...
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1answer
120 views

Can NATs and firewalls blacklist IPs when trying to UDP hole punch?

I am developing a P2P application that will make use of UDP hole punch to connect two peers behind NAT. When dealing with connections between a cone and a symmetric, unpredictable NATs, however, hole ...
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2answers
387 views

Long character sequence in first string of HTTP GET request breaks the web service's HTTP response. Buffer overflow?

During my current security audit test I've stumbled on something I can't possibly comprehend. The behavior exhibits signs of a buffer overflow in the target or in some intermidiate service (HTTP ...