A denial-of-service (DoS) attack is an attempt to deny service to legitimate users by sending extreme amounts of requests to a server.

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DDoS/botnet or what's going on, cloudflare.com?

This is small output from tcpdump -i re1 'port 25': 14:00:10.732034 IP cf-190-93-254-113.cloudflare.com.http > MY_IP.smtp: S 4234708404:4234708404(0) win 8192 <mss 1412,nop,wscale ...
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39 views

DDOS on port 443?

Recently my friend asked me whether his network is secure because he is setting up a game server on port XXX. I opened up Nmap on my linux machine and found port 443 opened. I tried to access ...
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38 views

Configure Router for better DDoS protection Actiontec MI424WR

So for the past month, my server has been attacked by script-kiddies three times. The server is mainly used as a minecraft server. I am getting worried that this is becoming an outbreak as many of ...
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28 views

How can I efficiently filter Dos packets? [duplicate]

I have recently been the victim of some Dos attacks. The facts : I received a very high amount of packets saturating my connection and preventing me from accessing the Internet during one hour ...
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145 views

Compromised Debian server sending DDOS attack

I have a server online that apparently has been compromised and it sends DDOS attacks to another ip. The system is a debian 7 server, hosting a few wordpress, joomla websites, and airtime to host a ...
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50 views

Protected from attacks through Skype

I know that people can find your IP through Skype and try to DDOS it and take your Internet down for a couple of minutes or hours. What I would like to know is: How many people need to DDOS you at ...
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565 views

Linux message: Possible SYN flooding on port 25. Sending cookies

I have a Linux CentOS server online. At my console this message appeared: possible possible SYN flooding on port 25. Sending cookies. See SYN flood and SYN cookies. I have done an Apache JMeter ...
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80 views

Block Google Docs from retrieving file on website - Stop Google DDOS [closed]

I was reading a very interesting article on how someone used Google Docs to preform a DDOS attack on a website. They basically filled a Google Docs Sheet with =image() requests to download a certain ...
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49 views

How to mitigate IP fragmentation attacks before reassembly when authentication information is available?

I'm trying to filter incoming traffic to high bandwidth, low latency network, to mitigate DDOS. The incoming traffic is custom UDP (I'm setting the protocol specs so I can force IP headers if ...
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32 views

A lot of random NAT tables appear

My brothers Mac seems to be infected. It keeps on sending UDP and SYN floods to our router, and it multiplies my ping 10 times.When I look in the NAT Mapping table there are a lot of random address ...
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54 views

Block packets by size in Windows

currently I am receiving an attack against one of my services running on Windows Server 2008 R2 with malicious UDP packets all of a specific length. I have tried dropping these packets with a plugin ...
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80 views

Can Torrent/DHT network remember my IP?

I suspect that my torrent activity casted some sort of "natural" DDOS attack on me. I had UPnP configured and each time I was starting uTorrent client, it was generating new random port and was ...
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286 views

Firewall best practice

I have to implement a firewall on a Mikrotik RouterBoard. What is a good way to do it? Here is my plan: Note: We are using an OpenVPN (bridge mode) server, a DHCP server, a PPPOE client, and an NTP ...
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242 views

Measure DDOS attack strength

I have been puzzled on this theory. Assume Server B is sending DDOS attack to Server A, so is it possible for a random client A, to be able to measure the attack strength, like the client A was able ...
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2answers
110 views

Can a home user behind a firewall be targetted by a DDoS attack?

I've read about an attack that targets simple home computer users who are playing online poker: Players A and B join a real money 1 on 1 tournament. You cannot unregister from this tournament and if ...
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1answer
120 views

Remove Windows 8 Nag (which executable to delete?) [duplicate]

I'm currently experiencing a Windows 8 DoS. When this nag ribbon is open, I cannot use the machine: I've tried closing the ribbon with ESC, ALT+F4, and a few others that used to close programs. I ...
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1k views

Is /root/b26 a DDoS process?

I have found this process: /root/b26 Here is a top: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 20810 root 20 0 339m 808 360 S 100 0.0 27:39.95 b26 I have ...
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67 views

Can I authenticate multiple times to one access point?

I'm attempting to test the security and stability of a new wireless access controller and assigned, it a has a /24 subnet of IP addresses to use for giving clients DHCP. I'm wondering if its possible ...
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1k views

DDoS attack on SMTP

I am not sure whether this is the right place to ask this. But now I am in a great difficult situation. Our server is undergoing SMTP DDoS attack. The mail service has been totally down. We have ...
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2answers
152 views

Why is preventing DDoS so hard? [closed]

I was thinking, if a DDoS attack can come in 2 ways: Sending large packets. Sending many packets. Why don't network administrators limit IP connections, to let's say 3 users/IP's and set a limit ...
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2answers
228 views

VPS hosting and DDoS attacks prevention

I'm curious if there is any way to create such a network so that if one machine is hosting a couple of VM's and one of the VM's gets attacked, it doesn't take down the network. Is there anyway to do ...
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1answer
139 views

If someone downloaded 600GB , can that be a DOS attack

Last night someone exploited some vulnerability in my site and then upload a PHP script to my images folder. I have an Amazon EC2 server with CentOS. Then the hacker downloaded 600GB and increased ...
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1answer
150 views

What this command :(){ :|: & };: does? [duplicate]

What does this shell command do in Linux :(){ :|: & };: How can it be used in Denial of Service attacks?
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2k views

Wireless router lods reporting loads of DoS attack attempts

We're having intermittent connectivity issues with our ADSL at the office. We've been dealing with our ISP for weeks and they don't know how to fix our problem. What happens is that at multiple times ...
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1answer
577 views

Was this a DoS, a hack attempt, or something else?

I ssh'd into my home server earlier because it was taking strangely long to respond to HTTP requests. I noticed that the shell prompt was also acting slow. So I typed top, and saw several instances of ...
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754 views

Logging incoming IP addresses on a specific port

I've tried tcpflow and iptables but I'm unable to do so. I believe someone is attempting to DDOS my open port which is a server, so that my clients are unable to connect. From tcpflow I'm able to get ...
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121 views

Better configuring my firewall for Minecraft

Not long ago I purchased a new server, and I'm planning on running a Minecraft server on it. Now I'm trying to better configure my firewall to stop DDoS attacks on my server while running the ...
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220 views

DDOSED, Static IP but ISP says dynamic

I'm having a problem, sometime I'm getting ddosed for no reason (I verified with commview,wireshark). The first time I noticed I didn't think it was a problem because I was pretty sure my ip was ...
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254 views

How do I drop the entire INPUT chain from iptables?

On Linux, I've been building a malicious IP list. I assume the DDOS is now gone. How do I drop the entire INPUT chain from iptables, without affecting the FORWARD or OUTPUT chains?
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How to solve DDOS attacks in Windows Server 2008 R2 / Windows Server 2012? [closed]

Any software for windows Writing custom (intelligent) microsoft windows firewall extension (C#/C++/C) Writing custom (intelligent) firewall for windows Installing nginx etc. on the same computer and ...
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242 views

MacBook Air gets added to Watchguard XTM-21W Appliance's Blocked Site List?

We have this issue where one of our MacBook Air (Mountain Lion) users is periodically getting added to the Blocked Sites list within our Watchguard XTM-21 Appliance (XTM21-W). Couple of questions: ...
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2answers
275 views

Can an attacker create a DoS attack by sending TCP data segments?

I know about DoS by TCP SYN segments & want to know can it possile a DoS attack by TCP data segments?
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300 views

GoDaddy is attacked by Anonymous. Any way to bypass the DDoS to access email? [closed]

GoDaddy is attacked by Anonymous. Any way to bypass the DDoS to access email? We have all our email hosted and need access to it to operate.
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370 views

Route gameserver traffic through cloudflare? [closed]

I use cloudflare for my website and we have a gameserver I was wondering if it is possible to route traffic through cloudflare. This recently sprung into my head when I realized that I could route ...
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1answer
124 views

My server got ddos and now it is end. How can i debug further from logs [closed]

My server got 13 gbit ddos so leasweb nulled ip and the attack ended. My ip is still blocked and i got temp second ip. It is still not public. Now my question is how can i detect the attack from logs ...
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2answers
732 views

CSF/LFD - would I really need CPHulk enabled also?

So if I have the default configuration of CSF/LFD firewall running, should I enable CPHulk, or does CSF/LFD already do what CPHulk does? If the answer is "No, CSF/LFD does not do what CPHulk does", ...
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386 views

How to get rid of DOS attack: RST Scan?

I have Netgear Wnr1000v2 router. I have set my NAT to secure mode ( I don't know if that helps ). Many a times when I see my router's log I see lots of DOS attack: RST Scan. I somehow think that these ...
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2answers
782 views

How to force Apache to answer only to Cloudflare?

I'm sure you all know what Cloudflare is (it's a very famous CDN). What I want to do, is force my Apache HTTP server to ONLY answer to Cloudflare. I want Apache to ignore and close or not respond to ...
2
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1answer
210 views

Is it a DOS or DDOS if the attacking computers are on the same network

I'm currently doing a reflective report (reviewing someone else's work) for uni and the report is about DDOS. For the report the author carried out a DOS attack on a web server using computers that ...
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1answer
537 views

How come sites like Google/Facebook/etc. don't get DDOS'd even though they receive so many requests?

Something I don't understand: (Tens/hundreds of?) thousands of people simultaneously try to connect to a site like facebook.com or google.com. From what I understand, they must all necessarily ...
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2answers
4k views

How to detect DoS attacks / manually block IP on Ubuntu?

I have a VPS with Ubuntu. I host a small website (~10 visitors at the same time). Sometimes the website starts lagging. It lags so bad that my SSH connection starts lagging too. Running top says that ...
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2answers
3k views

How to find DoS attack source IP address in windows server 2008?

I have a windows server 2008 R2 which is victim of a DoS attack. How can I find out which IP is the source of attack? I have a anti DoS module on IIS 7.0 which works fine but it seems destination is ...
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432 views

Firewalling all incoming traffic with custom rules

How do you automatically block all incoming traffic by creating custom rule for every connection (in real time) using iptables? To clarify - the situation is that my linux box is being DDOSed via ...
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2answers
784 views

security of and the flaws of having open ports?

Ok, so, here is my my issue. awhile back, a friend wanted to grab some files from me, so I gave him my AFP (Apple File Protocol) address. Much like FTP SSH or SMB. Its cool for mac users and thats ...