How does it work?<\/strong><\/p>\nThe logistics of a DDoS attack may be best explained by an example.<\/p>\n
Imagine a million people (the attackers) get together with the goal of hampering Company X\u2019s business by taking down their call center. The attackers coordinate so that on Tuesday at 9 AM they will all call Company X\u2019s phone number. Most likely, Company X\u2019s phone system will not be able to handle a million calls at once so all the incoming lines will tied up by the attackers. The result is that legitimate customer calls (i.e. those that are not the attackers) do not get through because the phone system is tied up handling the calls from the attackers. So in essence Company X is potentially losing business due to the legitimate requests being unable to get through.<\/p>\n
A DDoS attack on a web server works exactly the same way. Because there is virtually no way to know what traffic is sourced from legitimate requests vs. attackers until the web server is processing the request, this type of attack is typically very effective.<\/p>\n
Executing the attack<\/strong><\/p>\nDue to the \u201cbrute force\u201d nature of a DDoS attack, you need to have lots of computers all coordinated to attack at the same time. Revisiting our call center example, this would require all the attackers to both know to call at 9 AM and actually call at that time. While this principle certainly will work when it comes to attacking a web server, it becomes significantly easier when zombie computers, instead of actual manned computers, are utilized.<\/p>\n
As you probably know, there are lots of variants of malware and trojans which, once on your system, lie dormant and occasionally \u201cphone home\u201d for instructions. One of these instructions could, for example, be to send repeated requests to Company X\u2019s web server at 9 AM. So with a single update to the home location of the respective malware, a single attacker can instantly coordinate hundreds of thousands of compromised computers to perform a massive DDoS attack.<\/p>\n
The beauty of utilizing zombie computers is not only in its effectiveness, but also in its anonymity as the attacker doesn\u2019t actually have to use their computer at all to execute the attack.<\/p>\n
SQL Injection Attack<\/h3>\n
![\"\"](\"http:\/\/www.howtogeek.com\/wp-content\/uploads\/2011\/11\/image55.png\")
<\/p>\n
What is it?<\/strong><\/p>\nA \u201cSQL injection\u201d (SQLI) attack is an exploit that takes advantage of poor web development techniques and, typically combined with, faulty database security. The result of a successful attack can range from impersonating a user account to a complete compromise of the respective database or server. Unlike a DDoS attack, an SQLI attack is completely and easily preventable if a web application is appropriately programmed.<\/p>\n
Executing the attack<\/strong><\/p>\nWhenever you login to a web site and enter your user name and password, in order to test your credentials the web application may run a query like the following:<\/p>\n
SELECT UserID FROM Users WHERE UserName='myuser' AND Password='mypass';<\/code><\/p><\/blockquote>\nNote: string values in a SQL query must be enclosed in single quotes which is why they appear around the user entered values.<\/em><\/p>\nSo the combination of the entered user name (myuser) and password (mypass) must match an entry in the Users table in order for a UserID to be returned. If there is no match, no UserID is returned so the login credentials are invalid. While a particular implementation may differ, the mechanics are pretty standard.<\/p>\n
So now let\u2019s look at a template authentication query which we can substitute the values the user enters on the web form:<\/p>\n
SELECT UserID FROM Users WHERE UserName=\u2019[user]\u2018 AND Password=\u2019[pass]\u2018<\/p><\/blockquote>\n
At first glance this may seem like a straightforward and logical step for easily validating users, however if a simple substitution of the user entered values is performed on this template, it is susceptible to an SQLI attack.<\/p>\n
For example, suppose \u201cmyuser\u2019\u2013\u201d is entered in the user name field and \u201cwrongpass\u201d is entered in the password. Using simple substitution in our template query, we would get this:<\/p>\n
SELECT UserID FROM Users WHERE UserName='myuser'--' AND Password='wrongpass'<\/code><\/p><\/blockquote>\nA key to this statement is the inclusion of the two dashes (--)<\/code>. This is the begin comment token for SQL statements, so anything appearing after the two dashes (inclusive) will be ignored. Essentially, the above query is executed by the database as:<\/p>\nSELECT UserID FROM Users WHERE UserName='myuser'<\/code><\/p><\/blockquote>\nThe glaring omission here is the lack of the password check. By including the two dashes as part of the user field, we completely bypassed the password check condition and were able to login as \u201cmyuser\u201d without knowing the respective password. This act of manipulating the query to produce unintended results is a SQL injection attack.<\/p>\n
What damage can be done?<\/strong><\/p>\nA SQL injection attack is caused by negligent and irresponsible application coding and is completely preventable (which we will cover in a moment), however the extent of the damage which can be done depends on the database setup. In order for a web application to communicate with the backend database, the application must supply a login to the database (note, this is different than a user login to the web site itself). Depending on what permissions the web application requires, this respective database account can require anything from read\/write permission in existing tables only to full database access. If this isn\u2019t clear now, a few examples should help provide some clarity.<\/p>\n
Based on the above example, you can see that by entering, for example, \"youruser'--\", \"admin'--\"<\/code> or any other user name, we can instantly login to the site as that user without knowing the password. Once we are in the system doesn\u2019t know we are not actually that user so we have full access to the respective account. Database permissions will not provide a safety net for this because, typically, a web site must have at least read\/write access to its respective database.<\/p>\nNow let\u2019s assume the web site has full control of its respective database which gives the ability to delete records, add\/remove tables, add new security accounts, etc. It is important to note that some web applications could need this type of permission so it is not automatically a bad thing that full control is granted.<\/p>\n
So to illustrate the damage which can be done in this situation, we will use the example provided in the comic above by entering the following into the user name field: \"Robert'; DROP TABLE Users;--\".<\/code> After simple substitution the authentication query becomes:<\/p>\nSELECT UserID FROM Users WHERE UserName='Robert'; DROP TABLE Users;--' AND Password='wrongpass'<\/code><\/p><\/blockquote>\nNote: the semicolon is in a SQL query is used to signify the end of a particular statement and the beginning of a new statement.<\/em><\/p>\nWhich gets executed by the database as:<\/p>\n
SELECT UserID FROM Users WHERE UserName='Robert'<\/code><\/p>\n <\/code>DROP TABLE Users<\/code><\/p><\/blockquote>\nSo just like that, we have used an SQLI attack to delete the entire Users table.<\/p>\n
Of course, much worse can be done as, depending the SQL permissions allowed, the attacker can change values, dump tables (or the entire database itself) to a text file, create new login accounts or even hijack the entire database installation.<\/p>\n
Preventing a SQL injection attack<\/strong><\/p>\nAs we mentioned several times previously, a SQL injection attack is easily preventable. One of the cardinal rules of web development is you never blindly trust user input as we did when we performed simple substitution in our template query above.<\/p>\n
An SQLI attack is easily thwarted by what is called sanitizing (or escaping) your inputs. The sanitize process is actually quite trivial as all it essentially does is handle any inline single quote (\u2018) characters appropriately such that they cannot be used to prematurely terminate a string inside of a SQL statement.<\/p>\n
For example, if you wanted to lookup \u201cO\u2019neil\u201d in a database, you couldn\u2019t use simple substitution because the single quote after the O would cause the string to prematurely end. Instead you sanitize it by using the respective database\u2019s escape character. Let\u2019s assume the escape character for an inline single quote is prefacing each quote with a \\ symbol. So \u201cO\u2019neal\u201d would be sanitized as \u201cO\\\u2019neil\u201d.<\/p>\n
This simple act of sanitation pretty much prevents an SQLI attack. To illustrate, let\u2019s revisit our previous examples and see the resulting queries when the user input is sanitized.<\/p>\n
myuser'--<\/code><\/em> \/ wrongpass<\/em>:<\/p>\nSELECT UserID FROM Users WHERE UserName='myuser\\'--' AND Password='wrongpass'<\/code><\/p><\/blockquote>\nBecause the single quote after myuser is escaped (meaning it is considered part of the target value), the database will literally search for the UserName of \"myuser'--\".<\/code> Additionally, because the dashes are included within the string value and not the SQL statement itself, they will be considered part of the target value instead of being interpreted as a SQL comment.<\/p>\nRobert'; DROP TABLE Users;--<\/code><\/em> \/ wrongpass<\/em>:<\/p>\nSELECT UserID FROM Users WHERE UserName='Robert\\'; DROP TABLE Users;--' AND Password='wrongpass'<\/code><\/p><\/blockquote>\nBy simply escaping the single quote after Robert, both the semicolon and dashes are contained within the UserName search string so the database will literally search for \"Robert'; DROP TABLE Users;--\"<\/code> instead of executing the table delete.<\/p>\nIn Summary<\/h3>\n
While web attacks evolve and become more sophisticated or focus on a different point of entry, it is important to remember to protect against tried and true attacks which have been the inspiration of several freely available \u201chacker tools\u201d designed to exploit them.<\/p>\n
Certain types of attacks, such as DDoS, cannot be easily avoided while others, such as SQLI, can. However, the damage which can be done by these types of attacks can range anywhere from an inconvenience to catastrophic depending on the precautions taken.<\/p>\n","protected":false},"excerpt":{"rendered":"
Even if you\u2019ve only loosely followed the events of the hacker groups Anonymous and LulzSec, you\u2019ve probably heard about web sites and services being hacked, like the infamous Sony hacks. Have you ever wondered how they do it? There are a number of tools and techniques that these groups use, and while we\u2019re not trying […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[33],"tags":[],"class_list":["post-376","post","type-post","status-publish","format-standard","hentry","category-sec-secops"],"_links":{"self":[{"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=\/wp\/v2\/posts\/376","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=376"}],"version-history":[{"count":3,"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=\/wp\/v2\/posts\/376\/revisions"}],"predecessor-version":[{"id":1201,"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=\/wp\/v2\/posts\/376\/revisions\/1201"}],"wp:attachment":[{"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=376"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=376"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=376"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
![\"\"](\"http:\/\/www.howtogeek.com\/wp-content\/uploads\/2011\/11\/image61.png\" "\\"image\\"")
<\/p>\n