The backdoor functionality of Grandoreiro includes manipulating windows; updating itself; capturing keystrokes; simulating mouse and keyboard actions; navigating browsers to chosen URLs; signing out and restarting machines; and blocking access to websites. Grandoreiro collects various information about affected machines and, in some versions, it also steals credentials stored in Google Chrome as well as data stored in Microsoft Outlook browsers.“For a Latin American banking trojan, Grandoreiro utilizes a surprisingly large number of tricks to evade detection and emulation. That includes many techniques to detect or even disable banking protection software,” says ESET researcher Robert Šuman, leading the team analyzing Grandoreiro. “They seem to be developing the banking trojan very rapidly. Almost every new version we see introduces some changes. We also suspect they are developing at least two variants simultaneously. Interestingly, from a technical point of view, they also utilize a very specific application of the binary padding technique that makes it hard to get rid of the padding while keeping a valid file,” adds Šuman.Unlike the majority of Latin American banking trojans, Grandoreiro utilizes quite small distribution chains. For different campaigns, it may choose a different type of downloader. These downloaders are often stored on well-known public online sharing services such as GitHub, Dropbox, Pastebin, 4shared or 4Sync.
For more technical details about Grandoreiro, read the blogpost “Grandoreiro: How engorged can an EXE get?” on WeLiveSecurity.com. Make sure to follow ESET research on Twitter for the latest news from ESET Research.
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