Concerned with software or hardware firewalls

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60
votes
6answers
25k views

What techniques do advanced firewalls use to protect againt DoS/DDoS?

It is hard to protect a server against Denial of Service attacks, DoS/DDoS. The two simple ways I can think of is to use a server with much resources (e.g. CPU and memory), and to build the server ...
44
votes
10answers
52k views

Why do people tell me not to use VLANs for security?

I have a network, where a have a couple of VLANS. There is a firewall between the 2 VLANs. I am using HP Procurve switches and have made sure that switch-to-switch links accept tagged frames only and ...
35
votes
4answers
43k views

Should SSL be terminated at a load balancer?

When hosting a cluster of web application servers it’s common to have a reverse proxy (HAProxy, Nginx, F5, etc.) in between the cluster and the public internet to load balance traffic among app ...
14
votes
6answers
15k views

How important is NAT as a security layer?

I've signed on to help a department move buildings and upgrade their dated infrastructure. This department has about 40 employees, 25 desktops, an old Novell server, and a handful of laboratory ...
71
votes
2answers
77k views

Is it a bad idea for a firewall to block ICMP?

This question was inspired by this answer which states in part: The generic firewall manifest file finishes off by dropping everything I didn't otherwise allow (besides ICMP. Don't turn off ICMP). ...
42
votes
9answers
60k views

Why block outgoing network traffic with a firewall?

In terms of a home network, is there any reason to set up a router firewall so that all outgoing ports are blocked, and then open specific ports for things such as HTTP, HTTPS, etc. Given that every ...
29
votes
7answers
8k views

Port Knocking is it a good idea?

Normally for a server I like to lock down SSH and other non-public service to only be accessible by certain IP addresses. However this is not always practical if the business doesn’t have static IP ...
19
votes
2answers
6k views

Reject IP packets with an ICMP error, or just drop them?

Consider an internet-facing host (the outer firewall). What should be done with undesired traffic: just drop it, or send back an ICMP error such as port unreachable? (In Linux terms: iptables -P DROP ...
8
votes
5answers
8k views

What kind of attacks against home router's NAT do exist?

I always thought NAT was some kind of a security feature and I still think it is, because if it didn't existed the internet, respectively the clients behind NATs, would be even more insecure, since ...
6
votes
2answers
15k views

What is best practice for separation of trusted zones from a DMZ with a single firewall?

At our organization we have a single firewall sitting between our internal zones and the public internet. Currently all of our trusted zones are defined as different vlans on a layer 3 switch plugged ...
15
votes
5answers
21k views

What is the best practice for placing database servers in secure network topologies

I have a classic DMZ architecture: My webserver is placed in the DMZ. The webserver needs to communicate with a database server. This database server is the most critical component of my network ...
21
votes
12answers
48k views

Public DMZ network architecture

Years ago, when I was a student, a network security professor taught me in a class what a DMZ is. The architecture he used in his slides was similar to this one: Now that I got employed, my boss, a ...
19
votes
5answers
3k views

To firewall or not to firewall?

There's recently been some discussion (to be generous) about the pros and cons of having a firewall deployed in front of servers. The con mainly being that it's a point of failure in case of a DDoS. ...
25
votes
4answers
11k views

Dangers of opening up a wide range of ports? (mosh)

Why do we generally configure firewalls to filter out all traffic that we don't specifically allow? Is this just an extra layer of security for defense-in-depth that buys us nothing if we are not ...
8
votes
3answers
2k views

Evasion techiques for WAFs

Is there any documented techniques for evading Web application firewall for testing WAF rule configurations.
8
votes
3answers
13k views

How to protect myself against paid DDoS services?

I am domestic user and I am getting attacked regularly by a guy that hates me. Here is the background story: that guy uses Skype resolvers (tools offered by paid DDoS services) to find out my IP ...
6
votes
7answers
9k views

What tools exist to manage large scale firewall rulesets?

For an enterprise firewall you may have over 50 thousand rules. With typical errors in firewall rules including things like mistyped network masks you couldn't hope to manually review the release. So ...
4
votes
2answers
302 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 ...
3
votes
2answers
256 views

Is it safe to not update Windows if you dont accept any incoming connections?

I see this guy shared his thought: How to be safe even without most updated Windows updates So he claims that as long as you do not accept any incoming connections and just use sandbox of Chrome, ...
1
vote
2answers
2k views

How to check if a port can be accessed from the outside

I want to be sure that the firewall protecting the intranet is effectively rejecting/granting access to a port. I have no access to the firewall nor any other external machine. Is that possible at ...
19
votes
5answers
83k views

Difference between IDS and IPS and Firewall

The differences between an IDS and a firewall are that the latter prevents malicious traffic, whereas the IDS: Passive IDS: the IDS only reports that there was an intrusion. Active IDS: the IDS also ...
18
votes
5answers
3k views

Neural networks & anomaly detection

Neural networks, with their ability to learn behavioural patterns from arbitrary data, seem like a natural way to deal with intrusion detection. There are many academic papers on the topic which ...
15
votes
2answers
224k views

What are the TCP/UDP ports used by torrent applications?

I want to block torrent traffic on my network because it is utilizing too much bandwidth and disrupted my network traffic. What port range should I use and what protocol TCP or UDP?
17
votes
1answer
4k views

What is a Web Application Firewall?

What is a Web Application Firewall (WAF) and what are some of the things to look for in an effective one? Why would you deploy a WAF instead of just an IPS?
26
votes
3answers
5k views

Is it practical to pre-blacklist certain GeoIP regions?

In recent events, a server I've been managing with has been under a few attacks, a risk you take when hosting a web-server. The firewall has been set up properly to only allow connections through the ...
10
votes
2answers
6k views

Kerberos authentication over the public internet

What are the threats to having the KDC accessible via the internet for remote clients? It's my understanding that the authentication is a challenge/response protocol and that the password is never ...
4
votes
3answers
211 views

Open ports with no services bound to them

I have been wondering: if a port is open for inbound connections on the firewall yet there is no service bound to it, would that be considered a security vulnerability?
19
votes
4answers
2k views

Detect non HTTP packets using port 80

We are currently doing port whitelisting on our firewalls which is working well but this of course does not prevent the implementation of side channels or the misuse of these ports for other purposes. ...
13
votes
7answers
3k views

Egress filtering on an office network?

With an office network most companies will use ingress filtering to add a level of security, however few take advantage of egress filtering to protect their networks. The use of egress filtering will ...
12
votes
3answers
13k views

Proxy vs. Firewall

I understand that very simply put a proxy is a sort of 'man in the middle' allowing/denying access to certain services/resources. Strictly in terms of security (I mean here privacy, parental control ...
2
votes
3answers
561 views

Security risk with using internal IP on public DNS

A web server inside the office network which is accessed by staff internally and the internal DNS resolves web.company.com to the server's LAN IP. Publicly, company.com nameservers belong to their ...
1
vote
5answers
90k views

How to effectivily block torrents on my network?

Hie, As per my network policy, we have to block all torrent traffic from network. To do this, I used to block all ports above 1024 on my firewall/proxy devices. But due to this, many other ...
13
votes
2answers
27k views

Wireless client isolation - how does it work, and can it be bypassed?

Many SOHO routers these days support a feature called "wireless client isolation", or similar. What this is supposed to do, in principle, is to limit the connectivity between wireless clients ...
8
votes
3answers
7k views

Block all BotNets and TOR addresses from accessing our site

I've heard that many DOS attacks and general "black hat hacking" attempts occur over the TOR network. Is it possible for me to dynamically block source IP's by their presence in a BotNet or similar ...
5
votes
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 ...
5
votes
4answers
2k 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 ...
3
votes
2answers
114 views

Reverse Proxy or direct?

imagine I have an architecture as shown. In order to get to the internal web server, should I use a reverse proxy like as shown and redirect traffic to my web server? Is this a more secure way ...
3
votes
1answer
650 views

Is it possible to force client use TCP instead UDP for DNS queries?

Assume I am managing a firewall between DNS server and clients. Is there any way to force clients use TCP rather than UDP, so we can prevent DNS spoof types of DDoS attacks?
2
votes
2answers
1k views

Firewall & TCP Traffic

I have a question regarding network firewalls and TCP traffic. When a firewall rule is set to block either inbound traffic, outbound traffic, or both on a port, does that only apply to initial ...
1
vote
2answers
7k views

How secure is blocking all incoming connections on my ADSL or cable router?

My router, an up-to-date ADSL Fritz!Box 7340 router with a fixed leased IP address, has been configured to block all incoming traffic. Assuming, for the sake of argument, no extra security is ...
0
votes
2answers
8k views

Trying to get rid of hackers who have access to all my devices [closed]

What is the best way to go about getting rid of hackers that have gained access to all my personal computers, (both old and recently purchased) phones, and even random computers I use to simply get ...
0
votes
1answer
3k views

What is the difference between SYN cookie, SYN cache, and SYN proxy?

I am trying to understand some techniques regarding SYN flood prevention and there are three terms I couldn't find a clear explanation of. The terms that are confusing me are: SYN Proxy SYN Cache ...
7
votes
6answers
322 views

Why shouldn't I run other applications on a Firewall?

If I want to use Ubuntu 11.04 as a Firewall in SOHO environment, then I just can't figure out what is the bad thing about installing GUI on it (e.g.: XFCE)? The only opened port to the world (wan ...
5
votes
2answers
3k views

incoming packets in server

I have enabled iptables logging for packets coming from the outside -A INPUT ! -s 192.168.218.0/24 -j LOG Now i am seeing lots of incoming packets from unknown addresses Jun 5 14:54:56 localhost ...
3
votes
2answers
417 views

Firewall egress filtering / quick whitelisting

Suppose your Aunt or Uncle is easily fooled by phishing attempts and their computer has multiple root kits and key loggers running. Assume their computing habits will never change. Looking at his ...
3
votes
4answers
438 views

What does a switched network protect us from? What does it not protect us from?

There seems to be some misconceptions regarding what a switched network will protect us from, and what technologies/precautions a secure environment requires when segmenting trusted users from hostile ...
2
votes
1answer
248 views

Maximum protection on a computer network?

I would like to secure as much as possible a computer I am using to sync sensitive data files from work to my home pc. The syncronisation is being done by only 1 software is there a firewall to allow ...
1
vote
2answers
2k views

IP Spoofing a threat?

Quick Security Question if i may. We have an internal Intranet system which is only accessible from a few internal vlans, our main external firewall blocks all access to the internal webserver – or ...
1
vote
1answer
136 views

Preventing outgoing Portscan/SYN/UDP Floods in the datacenter

We are a VPS hosting company that have servers housed in a datacenter in Germany. Currently we are receiving multiple take-down requests because customers are ports scanning or attacking servers ...
0
votes
1answer
2k views

Dual Firewall DMZ

We've just learnt about firewalls and DMZ and I'm struggling to understand how are these actually implemented ? The architecture we've learned was something like this: Let's say that we have a ...