Introduktion
Från och med maj 2012 börjar jag att publicera en kort sammanställning av säkerhetsläget på Windows-fronten. Denna dyker upp i samband med Microsofts månatliga patch-utskick, så räkna med ett nytt inlägg under den vecka som innehåller den andra tisdagen i månaden.
För mig är detta tillbaka till rötterna, då jag ansvarade för en liknande bulletin på mitt förra jobb.
Så hur är läget på säkerhetsfronten? Tja, om man tittar på de närmaste veckorna verkar den största nyheten vara det triviala sätt man kan attackera vissa php-installationer på. På grund av en sårbarhet i php, kan man i vissa fall köra kommandon med webserverns behörighet och identitet. För att en attackerare ska kunna uttnyttja sårbarheten måste anropen gå genom PHP-CGI-modulen. Om du vill testa en egen server, kan du prova att att lägga till ?-s till en av php-sidorna. http://localhost/index.php?-s. Om sårbarheten går att uttnyttja får du tillbaka skriptets källkod. Denna väg kan du köra vanliga shell-kommandon med webserverns behörighet. För en bulletin som rör säkerhetsläget för Windows, är det kanske lite märkligt att jag tar upp detta då sårbarheten kräver att servern är Linux/Unix-baserad. Men jag tyckte det var värt att ta upp i vilket fall.
Bulletiner
Kritiska
MS12-029 Vulnerability in Microsoft Word Could Allow Remote Code Execution (2680352)
MS12-031 Vulnerability in Microsoft Visio Viewer 2010 Could Allow Remote Code Execution (2597981)
MS12-032 Vulnerability in TCP/IP Could Allow Elevation of Privilege (2688338)
MS12-033 Vulnerability in Windows Partition Manager Could Allow Elevation of Privilege (2690533)
MS12-034 Combined Security Update for Microsoft Office, Windows, .NET Framework, and Silverlight (2681578)
MS12-035 Vulnerabilities in .NET Framework Could Allow Remote Code Execution (2693777)
Viktig
MS12-030 Vulnerabilities in Microsoft Office Could Allow Remote Code Execution (2663830)
Den goda nyheten för stunden är att det inte verkar vara några stora attacker på gång mot just dessa sårbarheter.
How to read a Microsoft bulletin
Då jag inte riktigt hunnit komma upp I varv med denna bulletin ännu, får ni stå ut med att jag återpublicerar ett blogginlägg från min privata blogg. Detta beskriver hur man läser en säkerhetsbulletin och är på Engelska.
If you read security bulletins, you’ll probably come across a number of terms that everyone just accepts. But how many of them do you really know? I’ve compiled the explanations from some of my other texts to give you a brief rundown of what you must understand when you read a Microsoft Security bulletin.
One bulletin may describe a fix for many vulnerabilities.
Maximum Security Impact
This category tells you what is the worst thing an attacker may be able to do to a vulnerable system.
“Denial of serviice”
An attack that causes a system to fail, stop responding or to slow down to a crawl is known as a “denial of service attack”. The most common way to perform this type of attack is to overwhelm the system with a large amount of repeated requests. A vulnerability that allows an attacker to take a whole system or service down by sending a few malformed requests is said to have “Denial of service” as its “Maximum Security Impact”.
“Elevation of privilege”
This category contains vulnerabilities which can be used to give an attacker more privileges and permissions on a system. The most common way this happens is when an attacker starts out as anonymous (not authenticated) and then uses an exploit to make himself an administrator. This is sometimes known as “rooting” a system after the Unix super user known as “root”. This category of attack can sometimes also be used to impersonate another user.
“Remote Code Execution”
A vulnerability that allows for users to run a program or script on a system when they’re not logged in to it on the console, is known as a “Remote Code execution” vulnerability.
“Information Disclosure”
Some vulnerabilities allow you to retrieve information that you normally shouldn’t be allowed to get. An example could be when you can read the contents of an asp-script or read files that require permissions you do not have.
Microsoft Exploitability Index
As all of you know, Microsoft rate their vulnerabilities on a scale ranging from low to critical. They call this the "Maximum Severity Rating". But it's far less common knowledge that they also have an "Exploitability Index" rating on every bulletin.
An example:
"MS09-036
Vulnerability in ASP.NET in Microsoft Windows Could Allow Denial of Service (970957)
CVE-2009-1536
3 - Functioning exploit code unlikely
A denial-of-service tool is likely. However, functioning exploit code for remote code execution is unlikely."
The Exploitability index for this vulnerability is 3, which is the lowest rating.
- A rating of 3 means the exploit code is unlikely work. It may cause an effect, but it will probably not work well enough to allow for something like remote code execution. Example: if the exploit only works 1 time out of 100 when you attack a system, it is not considered a stable exploit.
- A rating of 2 means that the exploit code work but will not be successful often enough to be considered stable.
- A rating of 1 means that the exploit code will work repeatedly.
Here’s the official guide to software updates from Microsoft:
http://support.microsoft.com/kb/824684/en-us
Länkar
ISC SANS skriver om månadens uppdateringar
http://isc.sans.edu/diary.html?storyid=13159
PHP släpper fixad version
http://isc.sans.edu/diary.html?storyid=13168
En mer djuplodande analys av php-sårbarheten
http://blog.spiderlabs.com/2012/05/honeypot-alert-active-exploit-attempts-for-php-cgi-vuln.html?utm_campaign=Feed%3A+SpiderlabsAnterior+%28SpiderLabs+Anterior%29&utm_medium=twitter&utm_source=feedburner