Concerned with software or hardware firewalls

learn more… | top users | synonyms (1)

3
votes
1answer
125 views

Who watches the watchmen? User empowerment over firewall behaviour on a personal computer

I've been exploring the gamut of free Windows firewall applications recently and have encountered the following problem: The better firewalls are excellent at stopping other apps from phoning home ...
3
votes
3answers
301 views

Security issues in a Dotnet Web application

I was required to fix three low risk security issues of a Web Application on a Windows 2003 server, NetFramework 2.0, IIS/6.0. It is tracert-able. That may assist for crackers to know network ...
3
votes
2answers
274 views

Can ipopts be used to circumvent a pf or iptables firewall source IP based blocking?

Can one use ipopts, and in particular IP source routing, to circumvent source-based blocking in pf or iptables? For example, with OpenBSD's pf: block in all # default deny block out all pass in on ...
3
votes
1answer
49 views

IPsec: Is AH in tunnel mode secure?

I have a site-to-site IPsec VPN which was performing poorly (10 -20% upload/download speeds as a percentage of available WAN circuit bandwidth) when using ESP in tunnel mode with DES encryption and ...
3
votes
1answer
119 views

Tracking down the source of email attacks

For the past week our company's IDS has been blocking 100-200 meeting invite emails per day from a specific client that are loaded with buffer overflows targeted at Exchange 2003. The payloads are ...
3
votes
1answer
595 views

Limit BitTorrent Sync connections to a specific network

Is it possible to limit BitTorrent Sync connections to a a specific network using the client software? Right now the closest I can come up with would be IP limitations imposed on each client using a ...
3
votes
3answers
1k 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 ...
3
votes
1answer
2k views

How can I find the process that is trying to use smtp to send email?

Previously I asked Who (which process) is calling curl? and I got very good answers (this answer in particular) which basically replace the curl binary with a shell script that logs each call to curl ...
3
votes
1answer
3k views

Is opening both TCP/UDP less secured than just TCP or UDP when needed and why?

If application needs opened port X UDP, or X TCP combination. Is there any potential risk by opening both UDP/TCP as I usually am not sure which one the application uses?
3
votes
1answer
3k 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: ...
3
votes
5answers
167 views

Windows: Any method to enforce user confirmation before the browser opens a URL requested by an external desktop app?

A robust outgoing firewall will protect against desktop applications directly connecting to the internet without your permission. However, as the browser is a generally authorized application for ...
3
votes
1answer
637 views

Isolate a Virtualbox VM from local network [closed]

I have the need to isolate a virtual machine created with Virtualbox from the local network but I need to provide internet access to that machine. It is the first time that I face this kind of ...
3
votes
2answers
3k 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 ...
3
votes
1answer
101 views

SYN scan, determining scan vs large file upload

In a system attempting to detect SYN scans, one technique is to analyze the rate of change of (network packets sent from victim host per second). Processes such as uploading a large file would not be ...
3
votes
1answer
430 views

SSL VPN placement strategies

I wanted to know the advantages and disadvantages of placing an SSL VPN with respect to CIA in different locations: with firewall within the internal network within the DMZ Any reference also ...
3
votes
1answer
189 views

Why strip accept-encoding?

It seems that there are multiple "security" products which strip or mangle 'Accept-encoding' headers, thus forcing non-compressed responses from HTTP servers. I've been trying to imagine if there's ...
3
votes
2answers
492 views

1 PIX firewall, 2 routers, 2 switches. Please answer a couple questions about hack lab

I bought a bunch of cisco equipment for a project and I got 1 PIX firewall 2 switches and 2 routers This is my plan for a topology but I am new at this so I need help. I am basing this off the ...
3
votes
1answer
622 views

IP address filtering vs web application security

We have a web application behind a firewall that requires no user authentication. If we open up access to this application via the firewall to a small list of IP addresses what is the risk of ...
3
votes
1answer
934 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 ...
3
votes
4answers
511 views

Find out what Linux software is trying to phone home

I have seen some suspicious outbound communications blocked on my VPS, which hosts a small experimental Web site, and want to find out which application is making the attempt. The server is running ...
3
votes
2answers
2k views

Blocking incoming traffic from privileged port (< 1024) to mitigate DNS DDos Amplification attacks

Hope someone can clarify. As I understand, in a DNS DDos Amplification attacks Multiple DNS queries are sent to a vulnerable name server with the source IP spoofed to that of the target server. The ...
3
votes
4answers
301 views

Enforcing personal firewall for OS X

We're currently doing PCI compliance, and one of the requirements is that mobile devices that have access to systems involved in processing card data have personal firewall software installed which ...
3
votes
1answer
625 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 ...
3
votes
1answer
1k views

w00tw00t.at.ISC.SANS.DFind iptables fix - abusable?

It's only an idea. I've recently logged that my server is scanned by w00tw00t tools. I found many solutions to this, such as use of apache mod-security, fail2ban, etc.. The one I want to speak ...
3
votes
1answer
751 views

Mac sending hundreds of packets to gateway

I've got a user on my work network who brings her personal laptop (macbook) in for work. They've been having some horrendously slow network issues on everything past that hub, so I did some packet ...
2
votes
4answers
21k views

How can attackers bypass firewalls? [closed]

I have read the Wikipedia article on firewalls but don't understand firewall security and how an attacker from the outside can bypass the firewall to hack target system. We all know it happens but ...
2
votes
6answers
942 views

How do I prevent data from leaving my network?

I have a network of about 10 computers and I want to prevent sensitive data and source code leaks. To achieve that, I would like to block all file uploading / attaching. What are the options ...
2
votes
3answers
6k views

What, specifically, does the Windows Firewall do?

My understanding of the situation is that, when the Windows firewall is off, every port on the computer (all 65535 of them) is fully open. This means that any application running on the computer can ...
2
votes
3answers
2k views

How to block the websites on client machines

In our office we are blocking sites like Facebook, Twitter etc.The problem is that some of the users bypass our proxy and firewalls through external proxy sites like www.youhide.com or ...
2
votes
4answers
1k views

Best way to push data to a client without being blocked by firewall

I'm asking this question here since I think people on this forum probably have the best knowledge of firewalls and routers. Say I'm designing a multi-player game and I want to push data to the client ...
2
votes
2answers
6k 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 ...
2
votes
2answers
379 views

Identify if files are being transferred from my computer over the internet

This may seem like a silly question to most, but... I recently has some spyware infected on my machine, which I have since gotten rid of. Using a couple of scanners (that come recommended on various ...
2
votes
2answers
199 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 ...
2
votes
2answers
308 views

Web Application Firewall Rules

For Network Layer Firewalls we have different sort of redundancy and consistency checks like rule shadowing, that can impact the performance of firewall. Do similar kind of checks can be applied on ...
2
votes
2answers
507 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 ...
2
votes
2answers
4k views

IPTables default security rules for a gateway/router?

On a router such as dd-wrt or tomato, what would be some default iptables rules? I am asking for rules on a router/gateway - For example; blocking SYN flood attacks, or XMAS attacks. The basic ...
2
votes
2answers
60 views

Expose the source code repository externally or allow VPN access?

To allow third party consultants, offshore developers and contractors working on the code, we can expose our Git repository externally. Or we can grant VPN access to the external parties and limit ...
2
votes
3answers
656 views

iptables: plaintext password protection

I'd like to find a way to block or restrict my access to the web-pages where my password is sent as a plaintext on the internet. Let's assume if I have the same password for all web-pages, is it ...
2
votes
3answers
948 views

Why block network ports?

There was another good question here on why you should block outgoing traffic: Why block outgoing network traffic with a firewall? But I was hoping to get an answer on why it is a good idea to block ...
2
votes
3answers
1k views

Reviewing IP(s) that has been blocked by firewall / router

Is there a best practice on how to review IP(s) that are blocked on firewall / router and determine if they are safe to be removed from banned list? Occasionally, the firewall guys see a high counts ...
2
votes
2answers
2k views

How to block network scans with pfsense?

I am using pfsense as firewall, and I would like to know how I can stop network scans from enumerating open services and ports. Thanks
2
votes
1answer
413 views

How can the Google web crawler bypass portals?

This is a situation that I have encountered on a number of occasions. I will conduct a web search in Google, a link to a file (.pdf for example) will take you to that file on the server. It opens up ...
2
votes
2answers
249 views

Are there “LAN IPs” on the internet?

I have a home-made web application and thought that an easy way to secure it's administration interface would be to simply reject all IPs that arent from 192.168... Is this viable? is it possible for ...
2
votes
2answers
1k views

Benefits of REJECT over DROP on a single PC

Recently I learned about the difference between DROP and REJECT in a firewall. I understand that REJECT is better because it closes the connection immediately instead of waiting for timeout as DROP ...
2
votes
2answers
3k views

IPTables DDoS protection working with per client IP address counter AND UDP

I am looking to protect LAMP server with a software, which will detect above average number of requests from single IP numbers (in this case DNS queries), and add these hosts to IPTables deny chain. ...
2
votes
1answer
210 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 ...
2
votes
2answers
1k views

Why is my firewall blocking on some files but not others?

I'm behind a corporate firewall which restricts access to certain urls and most downloads. The download restriction is mainly on .exe(but it allows some exe files to be downloaded and I don't know ...
2
votes
2answers
397 views

how to find out if a program sends data to internet (without permission)?

We have an application to save our customers data (some kind of CRM). This application has been written in Delphi and is a client/server application. This program apparently is sending out ...
2
votes
1answer
1k 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 ...
2
votes
1answer
195 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 ...