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.
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Can you prevent fork bomb on Windows?
On Linux i can set limits in /etc/security/limits.conf to prevent fork bomb. How can you prevent fork bomb like this %0|%0 on windows?
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19 views
DNS Server is flooded with localhost resolution
I have a public DNS server and can be accessible by anyone. Recently we have been flooded with thousands of DNS queries trying to resolve a "localhost" such as these:
Is this supposed to be intended ...
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1answer
37 views
Send packet to a machine behind router
Context
I'm learning how the internet works, and I am trying to send a TCP packet from my VPS to my computer.
My VPS has a specific public IP address so I can easily send from my computer to my VPS. ...
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2answers
353 views
limit max UDP bandwidth per IP using iptables?
'm using a VPS to host a VPN for DDoS protection, but I've been wanting to find a way to rate-limit UDP traffic per IP to prevent UDP floods. I'm looking for something to only allow X MBPS of traffic ...
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1answer
149 views
Blocking DNS amplification attacks on ipv6 with iptables
I'm running a small Pi-Hole DNS server on my VPS, and I have the following iptables rules enabled to stop the DNS ANY amplification attack:
*raw
-A PREROUTING -p udp --dport 53 -m string --from 40 --...
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1answer
108 views
Cloudflare 525 error code and port scan
Today, Cloudflare return code 525 for some https connections.
And I see many connections in iftop on the origin server. This connections - port scan.
I used iptables, and block all packets, not from ...
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1answer
34 views
This IP was already used for a trial - spaming admin email
I use amazon lightsail and I get a lot of generated emails saying:
"The IP .... was already used for a trial license on 2019-03-13"
Where the IP changes to different IPs. The emails are from my cron ...
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24 views
Turning off network during Incoming DDOS
Sometimes on a server of mine, there is unsolicited incoming traffic (mix of random ports & random protocols beyond tcp/udp/icmp also) which starts peaking at 1 to 2 GBit/s while the outgoing ...
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75 views
How to block fake IP adresses?
on my webserver I find in the apache-logfiles:
[Wed Jan 09 16:29:10.660069 2019] [:error] [pid 11705] [client 66.249.66.66:39066] script '/var/www/fairtragen/7327991037366506690.php' not found or ...
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1answer
450 views
Block requests in lighttpd made with HTTP/1.0 and only allow HTTP/1.1
I have a lighttpd web server that delivers PHP-generated webpages. This server is currently facing a lot of traffic due to a DDoS bot attack, and I am looking for a way to block or mitigate some of ...
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2answers
943 views
What happens to your connection / modem when you are DDoSed and how can you prevent it? [closed]
I want to learn more about how DDoS and DoS attacks affect the network and how you can prevent them. I know how they 'work' and why the network is overloaded but I still dont know if a router / ...
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1answer
50 views
Being ddos-ed or my VPS has been compromised?
VPS bandwidth was suspended due to over usage.
Didn't really promote my website at all cus it is still under development.
Installed IFTOP and below is what I have captured.
Any advice is greatly ...
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60 views
One machine on network switch seems to be killing network for others - Hacked?
I have been trying to setup a new headless Ubuntu server and I have been having all sorts of issues with crashes and server no longer being available. I initially thought that these were hardware ...
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2answers
56 views
Checking if a router is online or offline?
Recently I've been receiving ddos attacks to my router, for educational purposes, I want to know how the attacker is finding out when my router has been ddosed.
They said they are doing something to ...
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0answers
56 views
Data security in server at home
I am a beginner linux user, and am planning on provisionally opening a game server on a machine I have at home. In addition to the possible DDoS attacks that may occur on this server (the server will ...
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1answer
622 views
Make Game Server DDoS-Protected
I'm a real noob in "server discussions".
Im running game servers on Debian 8 but the datacenter doesn't provide physical firewall, So Im looking for a way to make my servers ddos protected, I did ...
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1answer
41 views
How to generate normal web traffic for DDoS Testbed to compute the false positive rate?
I'm implementing an algorithm to detect HTTP GET Flooding Attacks. I have used Bonesi as a bonet traffic generator to launch attack traffic. However, I need a real trace of a normal web traffic (or ...
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1answer
2k views
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).
...
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50 views
Having too many ADPM and ICMP log in router admin panel
Recently, I feel that the speed of network became too slow. And I open router admin panel and have a look at the log messages. I found that there are many messages contains word "ADPM" and "ICMP", I ...
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1answer
230 views
Designing a custom small DDoS detection and defense sytem [closed]
Am very new to the topic so I would like some guidance where to get started.
What I want is, some tools to programmatically observe network traffic and preform some actions on the traffic. I don't ...
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2answers
4k views
Trying to understand anti TCP SYN flood attack IPTables rule
I’m currenlty working on a university assignment. I’m learning about firewalls and I need to configure IPTables on a Ubuntu machine to prevent a TCP SYN flood attack.
I understand that this type of ...
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1answer
4k views
What happens if the router is ddosed?
I don't know what happens if a router gets DDOS'ed? Does it brick it self or it just disables its ip? And if the ip disables its just easy fix by power cycling the router to get a new ip and getting ...
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1answer
68 views
Is there a way i can protect myself from DDOS attacks?
I got my IP spoofed somehow and how? Its because i visited a site which has a ip grabber and then a redirect to the site and my router is ADB and it has firewall but i don't think it won't help so i ...
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1answer
482 views
Am I under a DDoS attack?
OK, so here's some info:
Fedora23 running in VirtualBox on a Windows 7 Host.
Public-facing router has no DMZ, but port forwarding from 2325 (external) to 1194 (internal) and the internal static IP.
...
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1answer
3k views
Does Transmission Bittorrent client use UDP?
I am running a Transmission Bittorent server to upload various Linux ISOs.
I am currently being flooded by UDP packets. I mean the DoS protection in the Archer C5 home router and it blocks parts of ...
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1answer
1k views
I can access websites through the web browser, but I can not ping them or interact in various other ways
as of around two weeks ago I've been having really weird interactions with the Internet that I can't explain, but please keep reading. I've tried looking for the issue myself and haven't found ...
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1answer
57 views
How can I bridge my router to my Linux OS?
I am getting ddosed a bit so I want to send all my router traffic to my Linux OS as a somewhat mitigation. How to send my router traffic to my machine?
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1answer
718 views
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 ...
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1answer
2k views
Invalid URI in request and apache stopps working
Today our apache stopped working, he did not crash but stopped to response.
The only error i can see in the error_log is this:
[Thu Feb 11 10:00:05.245233 2016] [core:error] [pid 7496] [client 169....
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2answers
2k views
How virtual machines will be effected from DDoS attack on same physical server?
I mean let's suppose that there is a large DDoS attack to a virtual machine which is running on a physical server with other 10 virtual machines, how the other virtual machines will be effected from ...
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1answer
137 views
Firefox 43: Uploading to Youtube results in DoS behaviour
I've been trying to upload a video to my channel today, only to notice that Firefox starts using 100% CPU time on a single core and then suddenly, I and everyone in my household can't connect to the ...
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1answer
717 views
DOS attacks using cmd and protection against them
After finding someones ip you can easily send pings to them to make DOS attacks. Me and my friend tried to make a defense against them and wanted to know how a low level attacker can send this DOS ...
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2answers
67 views
Questions Regarding DoS
I have a few questions i still haven`t been able to get an answer to.
If someone DoS you, do it affect all computers connected to the router or just the computer that is being attacked? For example: ...
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1answer
207 views
Webserver accessible only from CloudFlare?
I wan't to avoid getting DDoSed as much as possible i can, so i thought if it's possible to set my web server to communicate only through CloudFlare. Any request from another source will be rejected, ...
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3answers
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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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1answer
4k views
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 ...
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1answer
1k views
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 ...
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2answers
202 views
Is it possible that I have caused a DoS to my son's tablets
I have three Internet connections at home, they are not connected to each other in any possible way, they are from three different ISPs
FTTC #1 , the white modem and the black and white router
FTTC #...
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3answers
2k views
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 ...
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1answer
145 views
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 8,nop,nop,...
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1answer
2k 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
https:...
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386 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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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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1answer
503 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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1answer
92 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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1k 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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0answers
526 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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0answers
109 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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0answers
744 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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1answer
263 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 ...
