Skip to main content

Hardening Adobe Reader 11 Using Group Policy

Due to its ubiquitous install base Adobe Reader (AR) has historically been leveraged by malware to facilitate infections.  Sandboxing technology implemented in AR11 largely addresses the problem. The sandbox has however been bypassed using flaw in AR’s JavaScript engine. AR has built in JavaScript engine that itself was the source of most security vulnerabilities in Adobe Reader. The JS is very rarely used in PDF documents and therefore it can be safely disabled.

With the release of version 11, Adobe has published a Group Policy template that can be leveraged to mitigate most of the avenues that attackers use to exploit our systems. 

The template files can be downloaded here:

They are provided in the standard GPO template format used since Windows 2008. There are two files: reader11.admx and reader11.adml. The files need to copied to different locations depending on whether you use local or central GPO stores. 

More information on GPO central store can be found here:

Supposing we use local store, .admx file should be copied to %SYSTEMROOT%\PolicyDefinitions 
and the .adml file to 

At this point we should see the following in Group Policy Management Console (GPMC):

It is important to note that computer level settings are actual GP settings. This means that users cannot alter the configuration. Also the settings are reverted to their defaults when policy is removed. User level settings are treated as preferences and as such can be altered by users. Also they do not revert to defaults when GPO is removed. 

Security wise we should consider enabling the following settings:

Computer Level>AR>Preferences>Startup: Enable Protected Mode at Startup 

User level>AR>Preferences>Security>Enable Acrobat JavaScript (we obviously want to set this to DISABLED)

As always do test the settings before large scale rollout.


Popular posts from this blog

x.509 Certificates - Critical vs non-critical extensions

Extensions are used to associate additional information with the user or the key.  Each certificate extension has three attributes - extnID, critical, extnValue extnID - Extension ID - an OID that specifies the format and definitions of the extension critical - Critical flag - Boolean value extnValue - Extension value  Criticality flag specifies whether the information in an extension is important. If an application doesn't recognize the extension marked as critical, the certificate cannot be accepted. If an extension is not marked as critical (critical value False) it can be ignored by an application. In Windows, critical extensions are marked with a yellow exclamation mark,  View certificate extensions using OpenSSL: # openssl x509 -inform pem -in cert.pem -text -noout (output abbreviated)         X509v3 extensions:             X509v3 Key Usage: critical                 Digital Signature, Key Encipherment             X509v3 Subject Key Identifier

DNS response and error types

In this post we explore common DNS response codes. We will cover the following responses: NOERROR SERVFAIL NXDOMAIN NODATA REFUSED Throughout article we’ll refer to the following RFCs: RFC 1034 - DOMAIN NAMES - CONCEPTS AND FACILITIES RFC 2308 - Negative Caching of DNS Queries (DNS NCACHE) RFC 2136 - Dynamic Updates in the Domain Name System (DNS UPDATE) RFC 8914 - Extended DNS Errors Response Codes - RCODEs The DNS RCODES are best defined in RFC2316 .  They signify what type of response was sent by the server. “RCODE   Response code - this four bit field is undefined in requests and set in responses.”   The table below shows the summary of the currently defined RCODEs. Mnemonic Val Description NOERROR 0 No error condition.

DNS blocking in Indonesia

DNS based censorship and domain blocking in Indonesia is very inconsistent among ISPs. There’s a government mandated black list which the ISPs operating in the country should enforce. However, Indonesia lacks centralised internet infrastructure and has many separate ISPs. In addition, the Indonesian government granted ISPs the authority to block content at their own discretion. All of this leads to a very inconsistent DNS blocking in Indonesia. Official DNS domain blacklist in Indonesia The Government mandated DNS blacklist is published in a redacted form and can be downloaded here: . This is where the blocked domains get redirected to. We can search the database and check if a domain is blocked. In the screenshot below we can see that a popular cryptocurrency exchange is blocked (Ada) and that is not (Tidak Ada) - thanks to Google Translate. Examples of blocked DNS queries dig @ ;; global options: +cmd ;; Got