The Stack Overflow podcast is back! Listen to an interview with our new CEO.

Questions tagged [denial-of-service]

Denial of Service is a family of attacks that attempt to force a target to use up resources (CPU time, memory, bandwidth etc) through flood a target with useless packets, connections or tasks

Filter by
Sorted by
Tagged with
147
votes
7answers
32k views

Can someone take down Wi-Fi signal?

Is it possible that someone made an attack (DoS or something else) to my Wi-Fi router (without knowing of the password) and make my router's signal unavailable? 1) How it can be done? 2) What are ...
92
votes
6answers
17k views

Is it safe to let a user type a regex as a search input?

I was in a mall a few days ago and I searched for a shop on an indication panel. Out of curiosity, I tried a search with (.+) and was a bit surprised to get the list of all the shops in the mall. I'...
65
votes
9answers
11k views

Can attackers get anything with DoS attacks except crashing the service?

A DoS (short for "denial of service") attack is a form of attack used on web services which aims to "crash" the service. Is there any motive of this form of attack besides crashing the service / ...
60
votes
4answers
10k views

I think I accidentally DoS'd a website. What should I do?

I was browsing a website, and stumbled across a sample scheme for password-protecting web pages. The owner of the website specifically had a page that invited people to attempt to hack it. I wanted ...
59
votes
2answers
14k views

How can ISPs handle DDoS attacks?

How can an ISP with low bandwidth like 50 Gbps handle a DDoS attack with more than this? I know there is a solution called "Black Hole". Is this enough to mitigate DDoS attacks or are there any other ...
57
votes
7answers
12k views

Does it make sense to consider a triggerable server software crash a DOS attack?

I've found a little vulnerability in a web application running on Node.js server. It works by sending some crafted payload to the application server, which makes the application server code to throw ...
57
votes
11answers
15k views

Can a DDoS attack yield any information?

Can a DDoS attack reveal any information or be used to mount a hack? My understanding is that the whole point of DDoS or DoS is to consume all of the resources/overload the server causing it to crash. ...
39
votes
3answers
34k views

Can I trust the source IP of an HTTP request?

As far as I've understood, if you try to issue a HTTP request with a spoofed IP address, then the TCP handshake fails, so it's not possible to complete the HTTP request, because the SYN/ACK from the ...
35
votes
6answers
20k views

Preventing artificial latency or “Lag Hacking” in multiplayer games

There is an attack that some people have dubbed "lag hacking", and its gaining popularity in multiplayer games. There are at-least two ways of creating artificial latency. One method of introducing ...
34
votes
3answers
3k views

Is there a security reason for a site to limit the number of times a user can change their password?

Is there a security reason to disallow a user to change their password as frequently as they want? I have found this security policy in a site and I am not sure why it is enforcing it. One reason I ...
30
votes
3answers
11k views

How do DoS/DDoS work?

In the last days one could frequently read about attacks from anonymous and LulzSec against different platforms like Sony or HBGary etc. Yesterday for example they DDoS'ed soca.gov.uk and jhw.gov.cn. ...
27
votes
4answers
9k views

Normal usage vs. denial-of-service? How many requests are needed to talk about a denial of service?

Recently I used a tool to download a website and as part of the tool one could adjust the number of parallel connections. So now I found myself asking: starting from how many requests a provider could ...
26
votes
5answers
3k views

Is unauthorised deletion an integrity or availability issue?

During a web application test I have discovered a parameter tampering issue that allows a user to delete comments left by other users. They can't modify the content of other users' comments, and they ...
26
votes
1answer
50k views

TCP Peer unexpectedly shrunk window messages in dmesg log

We get quite few messages like these in our dmesg log on various servers: TCP: Peer 0000:0000:0000:0000:0000:ffff:d431:5861:56369/80 unexpectedly shrunk window 2522304441:2522312601 (repaired) TCP: ...
23
votes
4answers
8k views

Protection against account lockout DoS

Any ideas on how to protect against the following scenario? Company x uses active directory for authentication of it's employees. The company has multiple authentication points that are semi-public ...
22
votes
4answers
11k views

Why does a (D)DoS attack slow down the CPU and crash a server?

So I get the basic idea of (D)DoS used for flooding, but I don't quite understand how this causes servers to crash or get them to slow down due to CPU overuse. As far as I know, the thing that is ...
22
votes
3answers
3k views

New denial-of-service vulnerability in TLS protocol, based on shooting down other users' sessions?

I think I have a new denial-of-service attack on TLS, and I'd like you to check whether this is a real vulnerability. I recently learned about the proper way to drop an authenticated client session (...
21
votes
3answers
2k views

Should you care about DoS attacks if your server is using bcrypt?

(I just asked this question on "cryptography SE" and was suggested to ask it here instead) EDIT I just realized my question is mostly a dupe of: Prevent denial of service attacks against slow hashing ...
20
votes
5answers
6k views

DoS in local network computer

I'm using Snort to study detection, and I wanted to simulate a DoS attack from the inside to another computer in my home network, but I have a question. If I start to flood the target computer with ...
19
votes
5answers
4k views

How can a DoS attack be used as part of the 'Gaining Access' phase of a hack?

I'm doing some revision for an exam and I've made a note to look at how DoS attacks can be used to gain access to a system. I can't find anything online but I found a reference to the fact here. I ...
18
votes
5answers
6k views

Cloud-based DDoS as a Service

With the consolidation of cloud computing and virtualization, a really simple doubt comes to my mind: why isn't DDoS being largely offered as a service? Why don't we see cloud-based DDoS attacks? ...
18
votes
4answers
814 views

Global Blackout is a myth?

In order to shut the Internet down, anonymous claimed that putting-down the 13 root DNS servers of the Internet and therefore disabling the HTTP Internet, the most widely used function of the Web, ...
18
votes
3answers
81k views

nf_conntrack: table full, dropping packet

I see a lot of these messages in /var/log/messages of my Linux server kernel: nf_conntrack: table full, dropping packet. kernel: __ratelimit: 15812 callbacks suppresse while my server is under DoS ...
17
votes
3answers
34k views

How can I block an IP, if I'm getting many http requests in a second?

If some one tried force burst attack on my website, how can I block them? Ideally, I want to block an IP if I have many http/Apache requests in a second.
17
votes
4answers
12k views

Best way to report a foreigner attacker's ip to authorities?

I have been under attack last week and I was able to trace down the attacker and get his IP address. The attacker was located in Germany but I live out of Europe? From your experience what is the ...
16
votes
6answers
9k views

What is a DoS Attack and how does it differ from a DDoS attack?

Can someone explain to me the concept of DoS attacks for web applications? Also, what is the distinction between DoS and Distributed DoS (i.e. DDoS) attacks? Wikipedia says: In computing, a denial-...
16
votes
5answers
10k views

What is the difference between login throttling and temporary account lockout?

I am currently working on the redesign of a login page. I have initially suggested that login be throttled whereby pauses (incremental - in number of seconds) are introduced between each failed login ...
16
votes
8answers
2k views

Bruteforce vs Denial of Service

I had a problem presented today which I found quite interesting. You have an application with a management panel. You know some of the accounts as they are standard. You want two things: You want ...
16
votes
5answers
24k views

How To Protect Tomcat 7 Against Slowloris Attack

I'm using Apache Tomcat 7 to run my webapp on Linux. I scanned it by Acunetix and it's telling me that my webapp is vulnerable to "Slow HTTP Denial of Service Attack". How can I protect it? Acunetix ...
15
votes
4answers
4k views

How to deal with this denial of service attack on an Apache server?

I was the target of different attacks today. The last one created this traffic on port 80. Apache is down and the load on server remains high. Firewall is enabled. Any suggestions? 15:27:10.203993 ...
15
votes
7answers
5k views

Prevent denial of service attacks against slow hashing functions?

I've been thinking about bcrypt recently, and what I wonder is if there's a way to deal with the inherent (D)DoS problems with slow hashing functions. Namely, if I set up bcrypt so my machine takes ...
13
votes
8answers
11k views

How does CAPTCHA mitigate DDoS attacks?

This seems like an easy question, but I've failed to find an answer. One of the uses of CAPTCHA is to cope mitigate Denial of Service attacks. Suppose an adversary performs excessive login attempts, ...
13
votes
1answer
10k views

how does a reflection attack work?

I am trying to understand reflection attacks but unfortunately wikipedia is too vague. I understand that in such an attack the attacker tries to authenticate with the target but does so in such a way ...
13
votes
4answers
10k views

How to perform a proper DDoS test in a safe and controlled way?

What is the proper and safe way to perform a DDoS test without crashing the whole infrastructure? What different types of DDoS attacks are there and what things should be considered performing such a ...
13
votes
2answers
8k views

Anti-DoS WebSockets Best Practices

What are the best practices for thwarting DoS attacks for a WebSocket server? Is there a comprehensive site or document that can be referenced?
13
votes
5answers
5k views

Apache/Linux server, DoS attack from own IP

I have an unusual problem I've been trying to diagnose for a while: It's about a Debian server running a custom compile of apache 2.2 with PHP, Red5, MySQL 5.5 (standard binary), sendmail (distro ...
12
votes
6answers
68k views

Google: “Unusual traffic from your computer network”

I often happen to receive the message: "Unusual traffic from your computer network" while googling in Russian speaking countries. Google explains this with: You may see "Our systems have ...
12
votes
4answers
7k views

mitigating anonymous DOS (tor combined with pyloris)

I found this rather scary video in youtube, that takes DOS to a whole new level, by making it look like coming from multiple sources. As a counter measure to Rsnake (Robert Hansen) slowloris.py script,...
12
votes
4answers
882 views

What lessons about Denial of Service can we learn from Egypt's “experiment”?

Internet service was widely disrupted in Egypt starting Jan 27th at about 22:15 UTC, in the space of about 20 minutes: How Egypt Killed the Internet. Service was largely restored 5 1/2 days later on ...
12
votes
1answer
2k views

Can/do botnets brute force “high value” users of services like Gmail?

On an intranet a login is generally disabled after a very small number of failed logins. But a public email service like Gmail can't do the same, otherwise pranksters would just be continuously ...
11
votes
4answers
5k views

How does HTTPS help websites under DoS attacks

From time to time one of the websites I browse regularly becomes a victim of a DoS/DDoS attack and usually they solve the problem by switching to https. I cant see the connection between the attack ...
11
votes
3answers
19k views

How to protect myself against paid DDoS services?

I am domestic user and I am getting attacked regularly by a guy that hates me. Here is the background story: that guy uses Skype resolvers (tools offered by paid DDoS services) to find out my IP ...
11
votes
4answers
5k views

How dangerous is it to allow arbitrary webhook urls to post to?

I am building a Ruby on Rails API that posts to webhooks that the API user can create, whenever a resource that he manages is created, updated or destroyed, using the HTTParty gem. This got me ...
11
votes
4answers
966 views

What are the drawbacks of login request throttling?

In a web application, one way to protect against password guessing attacks is to lock out accounts after a set number of failed logins. This could be done on both source IP address and username. For ...
10
votes
5answers
5k views

Is it illegal to DDoS a phishing page? [closed]

I used to go on a site called blockchain.info For storing bitcoins but today when I entered the URL I was redirected to a phishing page. I have entered all my information and it was obviously sent to ...
10
votes
3answers
3k views

Is there any way to stop DDOS attacks? [duplicate]

As many other webmaster I am facing problems with DDOS attacks. I have tried denying offending IP addresses from htaccess files and using bigger and better hosting, but I am unable to stop the attacks ...
10
votes
3answers
41k views

What are HTTP GET/POST flood attacks?

I want to know what the main differences are between HTTP GET and POST flood attacks and mitigation strategies for both. I searched a lot but I really can't find some good articles nor examples about ...
10
votes
2answers
8k views

Understanding Layer 7 DoS

I recently read this article about how a lone hacker (The Jester) conducts, amongst various other things, his DoS attacks over layer 7 instead of layer 4. It also mentions at one point he was able to ...
10
votes
4answers
26k views

Can someone launch a DOS attack on my IP

Suppose, I have a static IP on my PC and is known to others. None of my softwares listen for remote connection. Is it still possible for someone to DOS attack me in such cases? If yes, how it is ...
10
votes
1answer
6k views

How can I stop this DOS attack?

I have this entry appearing constantly in my router logs: [DOS Attack] : 5 [RST Scan] packets detected in last 20 seconds, source ip [xx.xx.xx.xx] They just never stop. It doesn't seem to affect ...