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57 votes
Accepted

What is the purpose of using random IP addresses in SYN Flood Attack?

A client opens a TCP connection by sending a SYN packet to a server. The server replies with a single SYN+ACK, and the client responds again with an ACK. Because of natural network latency, the server ...
forest's user avatar
  • 66.9k
20 votes

What prevents me from launching an SYN-ACK flood using HTTP servers?

This is a long known-about attack called a "reflected DoS". The reason it mostly doesn't cause much of a problem for defenders is that receiving an unexpected SYN+ACK doesn't take up any state on the ...
Polynomial's user avatar
  • 135k
20 votes

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

This is a classic SYN flood attack, preventive measures include hashing syn packets, implementing syn cookies checking if the client properly sends RST after an invalid packet sent back to him ddos ...
Rápli András's user avatar
10 votes

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

Limit NEW traffic sudo iptables -A INPUT -p tcp --dport 80 -m state --state NEW -m limit --limit 50/minute --limit-burst 200 -j ACCEPT Limit established traffic sudo iptables -A INPUT -m state --...
GAD3R's user avatar
  • 2,231
6 votes

What is the purpose of using random IP addresses in SYN Flood Attack?

A SYN flood can be more easily detected when the source of the attack is using the same IP address. So if a defender is detecting and able to block this activity you will not have a successful attack. ...
Michale Rezene's user avatar
5 votes

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

SOLVED In this case, it was a synflood attack with compromized Wordpress sites that generated tons of traffic (pingback) to our site at Gbytes/hour. Here is the full description of the attack. In ...
antony's user avatar
  • 309
4 votes

Is port in UDP flood necessary? HTTP flood-down because? UDP, SYN and ICMP flood methods

1- In flood scripts, the script sends UDP packets to "ip.address:random.port" Why It doesn't use only the IP ? Is port necessary ? UDP is a multiplexed protocol: it allows for multiple ...
GnP's user avatar
  • 2,279
4 votes

What is the purpose of using random IP addresses in SYN Flood Attack?

You double your traffic by not using your own IP. The response from the victim goes out to the IP you spoofed, who reply with a RST (subject to caveats). Being unpredictable makes them harder to block....
drjpizzle's user avatar
  • 199
3 votes

Hping3 doesn't work?

First off, if you spoof a source IP address, you will not get answers from the destination as the SYN/ACK packets go to the spoofed address. Other than that, if wireshark doesn’t show appropriate ...
Tobi Nary's user avatar
  • 14.4k
3 votes

Block SYN,ACK response with iptables

Blocking the SYN,ACK response is not the right way to go about SYN flooding. Every TCP 3-way-handshake starts with a SYN. If you block the SYN,ACK response, no client will be able to successfully ...
Demento's user avatar
  • 7,465
2 votes
Accepted

How to stop the flood of spam?

Google analytics traffic goes from the client browser to google's servers. this traffic does not touch your server. change your google anaylitics api key so that offenders using your old key will no-...
Jasen's user avatar
  • 1,226
2 votes

How to stop the flood of spam?

There are a few things you can do that might help. Add keyword blacklist to your site. If you get Trump and casino spam, drop any post containing the word Trump or casino. Add a rel="nofollow" to ...
John Deters's user avatar
  • 34.2k
2 votes

Why MSS is needed in SYN cookies?

This has something to do with MTU and Path MTU Discovery (PMTUD). Let's assume your MTU is 1400 and MTU of your server is 1500. When you try to download the file, without MSS or PMTUD, server would ...
Aria's user avatar
  • 2,701
2 votes

What prevents me from launching an SYN-ACK flood using HTTP servers?

In most ISPes or organisations your attack may not work for the outside, simply because it is considered a best practice of the industry and good etiquete to do what Cisco parlance call egress ...
Rui F Ribeiro's user avatar
2 votes

Question about ipsec prevent SYN flooding attack

IPSec does not prevent SYN flooding. IPSec is a VPN at the network layer (i.e. IP) and not the transport layer (TCP, UDP). It will transport any IP packets and not look deeper. But since SYN is a ...
Steffen Ullrich's user avatar
1 vote

Why does hping3 test DoS not successfully?

Without much more information on the specific site etc., the most likely cause of your failure to then access the site is that you were blocked. This is a very common defence mechanism: spot denial of ...
Rory Alsop's user avatar
  • 61.5k
1 vote
Accepted

Why are some Bluetooth devices susceptible to ping floods and some are not?

This is a type of Denial Of Service attack. You need to exhaust the resources of the victim in order to make a successful attack. The memory on a smartphone is way more than that of a Bluetooth ...
positron's user avatar
  • 165
1 vote

Is there any working solution against large SYN Flood request?

Cloudflare should terminate all connections and thus prevent these spoofed syns from arriving at your server. Appears to be a misconfiguration since this traffic is being seen at your server. Per ...
phbits's user avatar
  • 1,052
1 vote
Accepted

DNS flood vs DNS Amplification attack: How is one considered a network/transport layer attack and the other a application layer attack?

Yes, you've understood it correctly (except for a few details, see below) and the authors of the survey you've linked to are wrong. Or at least, if they have even really had some bright idea behind ...
ximaera's user avatar
  • 3,486
1 vote
Accepted

Are NTP servers without monlist still dangerous?

I think that the monlist is used for amplify the attach basically, so no the case of amplification attacks I don't think is a problem, however, the NTP servers could still be used for DoS attacks but ...
camp0's user avatar
  • 2,267
1 vote

packets characteristics (src,dst ports) of a DDos amplification attacks

For an up to date list of protocols used for DDos applification attacks, see UDP-Based Amplification Attacks Currently the list is +------------------------+--------------------------------+---------...
Dijkgraaf's user avatar
  • 473
1 vote

Hping3 doesn't work?

1) if your source machine have an IP as 192.168.100.1 and you spoof your source IP to 192.168.100.88, then the local tcp/ip stack discards the packet because you are not what you claim to be. (meaning ...
Laxmana Polisetti's user avatar
1 vote
Accepted

Mitigate DDoS attacks by randomly blocking traffic during the period of detection process

DDoS is a synchronous attack from many points. So there are no such things as "finding attacker address and stop them". If the attack appears to be hijacked IoT(e.g. Mirai botnet), you still has a ...
mootmoot's user avatar
  • 2,407
1 vote

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

The output you are showing suggests you are receiving a flood of SYN packets and not responding to any of them. Extrapolating from the numbers shown it amounts to about 7.5kpps. Even assuming a ...
kasperd's user avatar
  • 5,472
1 vote

Hping and spoofed DDoS (or DoS?) what do -U and -P mean?

Why do I need these flags? For generating SYN flood, you really don't need these flags (i.e., PUSH and URGENT flag). What's more important, what's their purpose? These flags are part of TCP header ...
Gaurav Kansal's user avatar
1 vote

Hping and spoofed DDoS (or DoS?) what do -U and -P mean?

No as far as syn flooding is considered you don't need those flags .. these flags are pointless when there is no tcp payload Syn in all standard implementation of TCP/IP stack are packet with empty ...
Arjun sharma's user avatar
1 vote

What prevents me from launching an SYN-ACK flood using HTTP servers?

It might work, but it seems painful. If I got you right, the naked SYNs on your "reflector" machine would eventually be identified by any IPS or modern firewall as an attempt to flood and would be ...
mgjk's user avatar
  • 7,525

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