Tagged Questions

Concerned with software or hardware firewalls

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14
votes
4answers
12k views

How are spoofed packets detected?

My assumption: When a firewall is configured to drop spoofed packets, it tries to ping (not necessarily ICMP) the source IP and sees if it belongs to a real host or if it's up, and if not, it drops ...
2
votes
1answer
248 views

Normalizing Windows Advanced Firewall rules

How can I best normalize our Windows Advanced Firewall rules while implementing network segmentation? I want them to be as clear and concise as possible for audit purposes. What few examples I've seen ...
0
votes
1answer
2k views

icmp packets not able to reach the firewall despite of adding a specific rule, why?

I am using iptables to allow the icmp traffic in/out of my host. Please find below are the entries from my firewall (linux based):- [root@localhost ~]# iptables -L Chain INPUT (policy DROP) target ...
2
votes
3answers
4k 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 ...
1
vote
2answers
2k views

What justification is there for Comcast to block SMTP port 25 outbound from residential service?

Within the last week, Comcast seems to have started blocking port 25 outbound from their residential internet service. I can sort of understand why they might justify blocking it inbound as perhaps ...
1
vote
3answers
1k views

Best practices for firewall hardware

I'm planning to implement a linux based firewall/router with at least 6 x 1Gb NIC's (network with ~300 computers/server with >=8 VLANs) Can anybody recommend hardware best practices (reference to ...
0
votes
1answer
3k views

Websocket implication for firewalls

(I've read several questions here about websocket but apparently there's no websocket tag) If I understand correctly websockets are using TCP trafic over port 80. What are the implication, if any, ...
5
votes
2answers
347 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 ...
3
votes
1answer
232 views

Blacklisting during a penetration test?

So i had a debate recently where one of my colleagues believed that by launching a penetration test (one requested by our clients) from our one of our IP's we could potentially get that IP/all IP's in ...
0
votes
1answer
75 views

Situations that a firewall should use rule for all packets

When should a "match all packets" rule be used (instead of chain policy)? I think that this should be used in real time applications like audio streaming or video broadcasting. Are there other ...
1
vote
1answer
224 views

Packet-filtering firewall evasion (Scanning)

Context I'm very familiar with different applications of scanning tools (. . . and you can use -mtu to specify the size of the fragments in nmap . . .) but every piece of information I read about ...
2
votes
2answers
2k views

What is more risky? Database Server in DMZ or Trusted Network?

Hoping this is not a dupe of any of the related database / DMZ questions, but I don't think any of them answered my question sufficiently. Assume the following A web server is being used for ...
3
votes
2answers
210 views

How to red team against firewalled architecture?

Prior Knowledge I understand the types and differences between firewalls. I have (what I believe to be) a relatively good mental model of a firewall. I understand routing, iptables, signature ...
1
vote
1answer
278 views

What are the basic implementations that make a network secure from the inside\outside?

Would you consider the following to be "basic hardening items" for network equipment and servers? VLANs Access Control (such as NTFS permissions) Patch Management System Host Firewall Anti-Virus ...
15
votes
3answers
15k 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 ...
3
votes
3answers
2k views

why blocking incoming traffic does not block chatting or VOIP

I just recently blocked all incoming traffic(all local ports and all external ips) in my windows 7 firewall and I understand that will not stop me from accessing websites as browsing needs outbound ...
6
votes
2answers
219 views

Firewall on a VM

I know I could use a software firewall on the guest to achieve a situation similar to this, but is there a way to emulate a firewall (protecting multiple Guests) between a host and guests on a ...
6
votes
2answers
184 views

Are temporary blocks sufficient response to network probes?

We have the option of using an automatic blocking feature of our firewall to temporarily block the source IPs of network probes. It is fast and automatic, and it expires after a set amount of time. ...
1
vote
4answers
997 views

Connections through Firewalls explained

I'm looking for a good explanation of how connections work through firewalls. I've got the idea of packaging(encapsulating) some protocol inside another one as its payload when tunneling. But what I ...
3
votes
1answer
464 views

HTTPS form submissions are blocked on corporate networks

We have an HTML form which is submitted via HTTPS. We've noticed that when the form is submitted on a home network, it seems to go through just fine. However, when the form is submitted on certain ...
2
votes
1answer
95 views

Quick Security Mitigations to Impending attacks

Suppose you are the sysadmin, and you know of an impending attack that just started or about to start soon. You can either wait it out, or try a few tricks and quick mitigation to fend off attackers ...
2
votes
1answer
916 views

Incoming Packet From Source Port 80

I'm sure no daemon or browser is using network resources, but I found incoming packets from Wireshark: 98.126.43.174 source port 80 --TCP--> MyIp destination port 339 [SYN, ACK] 98.126.43.174 ...
6
votes
3answers
2k views

Is it necessary to setup a firewall in both PC and router?

If I have the router firewall enabled, is it really necessary to setup iptables in my system? Isn't it a little redundant? For example I add a rule in the router where the PC can't use the port ...
1
vote
1answer
113 views

Guidelines on out-of-band server management via integrated Lights-out services (iLO, iDRAC etc.)

Several CVEs (CVE-2012-3271, CVE-2011-4158, and earlier) point out vulnerabilities in remote server administration firmware; what are the guidelines on hardening this extremely useful component of ...
0
votes
1answer
411 views

Weird issue with Firewall blocking NATed packets

From my SIEM I am seeing that a (we don't own the FW) Cisco ASA is blocking packets destined for the internal network (post NAT), here's what I'm seeing (IP addresses are faked due to security) ...
3
votes
2answers
209 views

Blocking executables at the firewall in the enterprise

The infrastructure team in our medium enterprise has requested blocking of all executables at the firewall. We have a firewall which is capable of DLP, so therefore this can be set up fairly easily. ...
1
vote
1answer
1k views

How to find IPS events in sonicwall syslog

I have a sonicwall os firewall, and the security dashboard shows about 9 intrusion prevention events in the last month. Most are called "Suspicious CIFS traffic 4". I have syslog servers setup with ...
2
votes
2answers
352 views

How to define different firewall rules for different users on the same machine running on Windows 7?

Provided that one machine running on Windows 7, connected to LAN, and connected to the Internet via a gateway in the LAN. There are two logon user accounts A and B on the machine. I want: 1, User A ...
11
votes
5answers
3k views

How can encrypted traffic bypass the Great Firewall of China when it is being blocked?

The Great Firewall of China is controlled by the government and has put in place a "learning algorithm" to block unapproved encrypted traffic. The only way to get encrypted traffic through the ...
3
votes
2answers
2k views

How secure is opening an incoming port for a java application?

If a java application is listening on UDP port xxxxx and a firewall is allowing connections to that java application through the same UDP port xxxxx, what vulnerabilities will a Windows 7 machine be ...
5
votes
2answers
2k 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 ...
2
votes
2answers
197 views

Access via http to other protocols and ports!

Our firewall only allows HTTP port 80 but we have detected that a user accesses some other protocols and ports that we deny in our firewall. We know that he has developed an application (Console ...
10
votes
6answers
740 views

Firewall philosophy

I've always been taught/believed that with a corporate firewall, you block all outgoing traffic to start, then open up only the holes you need for specific traffic. This makes sense to me from both ...
0
votes
3answers
412 views

Some issues with iptables and nmap

When I scan my pc with nmap I see only one open port. I didn't define any rule in iptables so if I'm not mistaken, all connections should be denied by default. However I can use HTTP or SSH, so that ...
0
votes
1answer
179 views

Windows Firewall accepts a three-second unicast response from any source

I have read this article but still has some doubts may be after that... The Windows Firewall feature in Microsoft Windows XP Service Pack 2 (SP 2) accepts a three-second unicast response from ...
15
votes
4answers
1k views

ESET warns: Skype attempting to communicate with unknown remote computer

I am frequently getting warnings from my ESET firewall, like that pictured below, that Skype is attempting to communicate over SSL with a remote computer that has an untrusted certificate: The ...
1
vote
1answer
119 views

Can a router detect transitive/cascaded telnet sessions?

I'm in my LAN segment , my desktops IP is x.x.x.x ; and I'm telneting to router A with its IP y.y.y.y from x.x.x.x .Now telnet session is established between x.x.x.x and y.y.y.y I want to telnet ...
-3
votes
1answer
7k views

windows firewall disabled with Norton Internet security or Norton Smart Firewall? [closed]

My Company decide to Change antiviruses and anti-spywares and firewalls. How to apply changes in all clients and servers safety? Norton say: ( in this article): When you are using Windows ...
4
votes
3answers
14k 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 ...
0
votes
3answers
4k views

why Windows Firewall in XP cannot block outbound connections

wikipedia say: XP's Windows Firewall cannot block outbound connections; it is only capable of blocking inbound ones. another article says: XP defends you with your traffic coming from the web but ...
4
votes
3answers
20k views

Windows Firewall - how to block inbound for all .exe files in a folder

In Windows Firewall with Advanced Settings I can create a rule which blocks all inbound or outbound traffic for particular program by pointing to its .exe file. The problem is that this program has ...
3
votes
2answers
3k views

If a port is closed how come you can still use it?

What does it actually mean for a port to be closed or stealthed? According to tests I've run all my ports (tested) are stealthed but clearly I can still use the internet. Also are the terms "blocked" ...
2
votes
1answer
209 views

What security risks are involved with sending data over the internal network on Rackspace Cloud servers?

What are the risks involved with sending unencrypted data over the internal network with Rackspace Cloud Servers? Assume the interfaces use iptables to filter IPs and ports so they only accept data ...
0
votes
2answers
308 views

can a backdoor executable be used on an occupied port?

Suppose I am doing a penetration test on a network that has a firewall that blocks all ports except 80, 110, and 443. I want to use a metasploit reverse-TCP backdoor executable written in msfpayload ...
32
votes
9answers
24k 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 ...
2
votes
1answer
189 views

Consequences of using -s and -d arguments in iptables

We are studying iptables for a Computer Systems Security course. We are confused as to what happens when the -s and -d arguments are both used in the same rule, such as: iptables -A OUTPUT -s ...
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 ...
5
votes
3answers
249 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 ...
1
vote
3answers
496 views

Testing Web Application Firewall Configuration (ModSecurity)

What is the best way of testing my Firewall configuration as i have deployed the Core Rule set provided by the OWASP. But my rule configuration was giving me too many false positives which i resolved ...
4
votes
5answers
14k views

How to bypass tcpwrapped with nmap scan

I'd a scan task and I faced following result Host is up (0.032s latency). Scanned at 2012-10-25 16:06:38 AST for 856s PORT STATE SERVICE VERSION 1/tcp open tcpwrapped 3/tcp open ...