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Questions tagged [denial-of-service]

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

A denial-of-service attack (DoS attack) is an attempt to deny service to legitimate users by overwhelming the server(s) and/or networks with a high number of requests. With some servers, a DoS can cause a system crash that may be classified as severe downtime.

When a DoS attack is orchestrated on a web server, the requests can elicit documents, images, videos, error pages, etc., which are intended to consume a high number of server and network resources to create the impression of an "outage."

For additional information about DoS attacks, see:

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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 connect to the same initial server (because DNS will…
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How ping a server which has ICMP blocked

I'm trying to ping a server which has ICMP blocked with normal ping. It's showing: Request timed out Is there any other method to ping it?
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Will the maximum speed of a network card reduce the impact of an incoming DDoS attack?

I’m wondering if the maximum speed of a network card would reduce the chances of a DDoS affecting a home-hosted website. In this scenario, I’m hosting my website from an Android Tablet where the maximum speed incoming/outgoing is 10mbps.
TheJamaicanGuy
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What is a safe ping frequency without it being considered a DDoS attack?

I am trying to chart the uptime of a server by regularly pinging it and Google and then comparing the ping times. I want to keep doing this over a period of—let’s say—a week. I am sending a set of 5 pings to each with a timeout of 5 seconds and an…
wsaleem
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What prevents unsolicited internet packets from using up my monthly data limit?

My home router can use port-forwarding to act as a server, so I assume all internet packets sent with my public IP address as a destination are hitting it (and just not getting any response from my router since I am not using the…
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Was this a DDoS, 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 sshd using a lot of CPU time. I checked…
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My home IP (supposedly) was involved in a DDoS attack

There did not seem to be any SO community dedicated to computer security, so I'll ask here... As the title implies, my home IP (supposedly) was involved in a DDoS attack. I got a phone call from a computer technician involved in a website, who said…
Manube
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What this command :(){ :|: & };: does?

What does this shell command do in Linux :(){ :|: & };: How can it be used in Denial of Service attacks?
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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", is there a way for me to change the CSF/LFD…
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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 2 instances of apache2 take up 50% CPU each. I…
Mikhail
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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 about it. He was really surprised that I was…
nick
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TP-Link DoS protection blocks Bonjour

We have an Apple-centric office and as such we rely on Bonjour (mDNS) for auto-discovery of things like printers, AirPlay targets, and pseudo-servers (e.g. exchanging files between desktop computers). I just installed a TP-Link T1600G L2+ switch as…
Old Pro
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Implementing fail2ban the correct way

I have a Django web app where people write comments and upvote/downvote others' comments. The webserver is gunicorn + nginx (reverse proxy). The db is postgresql. The db and web app reside in two different ubuntu-based machines. Some malicious users…
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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 necessary). Over which some authentication token can help…
darkblue
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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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