When it comes to DoS and DDoS, a lot of amateur hackers get the two mixed up when they have completely different meanings. Those who think they are doing a DDoS might actually be doing a DoS, or vice-versa. The reason they get mixed up a lot is because people don’t fully understand the terminology they are using, or they think they mean the same.
DoS (Denial of Service)
A simple DoS is when a network is sending out lots of packets that the server can’t accept (flooding), and it takes up the servers bandwidth making it either lag, not allow people to view the page, or shut down the server completely. That is what it is meant to do, but DoS, although can work, isn’t very effective. There are tons of programs out there that can allow you to DoS out there on the internet, but as it is only one network or computer the results are usually what you wouldn’t hope for. Even when multiple people are performing a DoS it usually doesn’t work all that well.
DDoS (Distributed Denial of Service)
A DDoS is when you have multiple servers or networks flooding packets into a single target at once (hence the Distributed in the title). This is usually acquired by either paying for the web servers, a bot-net, or you use a RAT to take control of computers and use them. The fact that this method is using multiple networks it is more effective then other methods, and it gets increasingly more effective for every network you are using. It aims to do the same thing as DoS but to a higher extent. DDoS is especially effective when more than one person is DDoSing the same target, and hacking groups like anonymous have used the fact that they have at their disposal many, many people who are able to DDoS a single server, therefore making this method, although harder or more expensive, more likely to achieve what you like.
The reason some people get confused is because people who want to be hackers are always trying to be like those really professional hackers you always hear about in the news. They hear about DDoS and they try to do it themselves, and thinking they have found it, they have actually found a DoS. Other reasons are because the two words are just one letter off from each other. And then there are just those people who are just plain stupid. I once had someone who said he could do a ‘Bandwidth DDoS’ which he said is “using your bandwith to hit someone”. The two problems with this is that it is not a DDoS, and that using your bandwidth to hit someone is exactly what you do with a DoS. People seem to always make their own words for things that are completely different to what it actually is, and the fact that people are doing this causes confusion among others who listen to those people.
Bottom Line: Don’t be an idiot, know the difference.