engaged_palladium_6461553e
conti_sample | 94bdec109405050d31c2748fe3db32a357f554a441e0eae0af015e8b6461553e
53.25 KB
PE Executable

Natural Language Summary

Likely Malicious

Verdict: Likely Malicious

Multiple strong indicators support a malicious classification: (1) per-directory ransom-note filename HOW_TO_DECRYPT.txt and extension marker .CONTI, (2) recursive directory traversal with file task scheduling, (3) large multithreaded network/target enumeration (32 threads), (4) runtime API resolution and heavy obfuscation to hinder static analysis, (5) payload launcher that executes embedded command blocks via CreateProcess with no window, (6) resource-driven configuration/payloads and lack of clear benign functionality. While exact per-file encryption routine is not visible in the provided excerpts, the combined capabilities indicate ransomware dropper/encryptor behavior with potential persistence actions in the executed payloads. Therefore, the verdict is malicious.


Summary

The binary implements runtime import resolution, a block-based XOR deobfuscation routine, an embedded configuration/payload dropper, and a multi-threaded target enumeration and file-processing framework consistent with ransomware behavior. It writes per-directory ransom notes, uses a marker extension .CONTI, excludes system folders, and orchestrates a 32-thread worker pool to operate across discovered IPs/hosts and target files. Embedded command blobs decoded at runtime via CreateProcess (hidden) indicate staged payloads and potential persistence mechanisms. Overall, the artifacts and behaviors are aligned with malicious ransomware tooling.

Orchestration

Central orchestration occurs in _start (0x402610). It resolves APIs at runtime (sub_4010e0), loads embedded configuration/payload data from RCDATA resources (IDs 0x68/0x69), decodes configuration (via the 128bit XOR key data_4099d0 using sub_401000) and compares against "null", then executes an execution-phase runner (sub_402bf0) and other initializers (sub_4032a0, sub_407fa0). It constructs target lists (hostnames via sub_4024b0 and IPs via sub_402990) and schedules per-target work through sub_407fe0, before final orchestration and cleanup via sub_408c50 and ExitProcess. The worker pool is initialized by sub_408bd0, with threads started in sub_408c10 and tasks enqueued by sub_408ca0; control messages are dispatched by sub_408c50 and wait-for-termination logic is in the same path. The overall flow is designed to be opaque statically, but functionally implements discovery, per-target task scheduling, and payload execution.

Installation

Embedded configuration/payloads are stored as RCDATA resources (IDs 0x68 and 0x69). _start loads both resources and decodes one with MultiByteToWideChar, comparing the decoded content to the string "null" to decide if a payload should be executed. The binary decodes multiple embedded command blocks and passes them to CreateProcessA/CreateProcessW with CREATE_NO_WINDOW, effectively acting as a dropper/launcher for secondary payloads. No explicit registry autostart artifacts are visible in the provided code paths, but decoded command lines could install persistence via subsequent payloads.

Persistence

No explicit Windows autostart mechanisms (registry Run keys, scheduled tasks, services) are visible in the provided functions. The presence of decoded command strings executed via CreateProcess suggests a high likelihood of persistence mechanisms being installed by the executed payloads (not visible in the supplied code). Follow-up decoding of embedded command blocks is required to confirm persistence techniques.

Code Protection

Strings and API names are obfuscated. Runtime API resolution uses decoded names via GetProcAddress (sub_4010e0), and a block-based XOR deobfuscation routine (sub_401000) applies a 128bit XOR with data_4099d0 followed by a single-byte XOR of trailing bytes (0x99). The import table appears empty statically, increasing analyze difficulty and hindering static linking of APIs.

Environment Awareness

No explicit anti-debug/VM checks are evident in the provided functions. However, the dynamic API resolution and heavy obfuscation imply anti-analysis intent by complicating static disassembly and import tracking. Additional anti-analysis checks may exist in code regions not provided here.

Runtime Behaviors

Entry path resolves imports, loads resources, decodes configuration and payloads, spawns a set of worker threads, enumerates hosts/IPs, and schedules per-target file tasks. A multithreaded executor processes tasks (likely file modifications) across a target list, with a separate process launcher (decrypt_embedded_command_blocks_and_execute_sequentially) that decodes and runs command blocks via CreateProcess in a hidden window.

Network Communication

The binary enumerates IP addresses and host names via resolved helpers (likely iphlpapi/netapi32-style interfaces). It uses InetNtopW to stringize IPs and maintains a global list of targets, then processes them via 32 worker threads. This pattern suggests network scanning, propagation attempts, or remote service interaction against discovered targets.

Data Handling

Files are enumerated recursively. The directory walker writes a per-directory HOW_TO_DECRYPT.txt and enqueues per-file processing tasks. It supports blacklist/whitelist modes and uses a token list (data_40ce88, data_409940) to filter targeted files. The behavior indicates intent to modify many user data files in place (likely encryption).

Cryptography

The code uses a repeating 128-bit XOR key (data_4099d0) to decrypt embedded payloads and strings, combined with a single-byte XOR (0x99) on trailing bytes via sub_401000. This obfuscation is used for hidden strings/payloads rather than strong cryptography for victims. No cryptographic primitives for file content encryption are visible in the provided paths, though a later stage (e.g., worker tasks) is likely encryption-based.

Credential Access

No direct credential dumping (LSASS, keychain) is evident in the provided functions. The network enumeration could enable credential-exploitation or lateral movement when paired with additional payloads, but explicit credential theft capabilities are not shown here.

Destructive Actions

The presence of per-directory ransom-note creation (HOW_TO_DECRYPT.txt), a marker extension (.CONTI), and the scheduling of per-file processing tasks imply encryption or modification of user data as the primary destructive action. The exact encryption method is not visible in the supplied code, but the pattern matches ransomware behavior.

Build Quality

Modular and well-structured, with clear separation of concerns (resolver, decoder, enumerator, worker pool). The use of data-driven resources, dynamic API resolution, and a reusable XOR deobfuscation routine indicate deliberate engineering. Error handling appears present, and the multi-threaded worker design points to performance-minded implementation.

Platform Specific Notes

Windows-targeted, using Win32 APIs (CreateProcess, thread creation, directory enumeration wrappers, InetNtopW), wide-character processing, and resource loading. It leverages dynamic API resolution to conceal imports, consistent with Windows malware tooling. It uses RCDATA resources for in-binary configuration/payloads.

Indicators

Type

String

Value

HOW_TO_DECRYPT.txt

Referenced By

sub_407fe0 (0x407fe0)

Indication

Ransom-note filename; canonical ransomware artifact written per-directory.

Type

String

Value

.CONTI

Referenced By

sub_407fe0 (0x407fe0)

Indication

Marker extension; likely used as extension appended to encrypted files. Presence strongly suggests ransomware family naming ('conti'-like).

Type

String

Value

Windows

Referenced By

sub_407fe0 (0x407fe0)

Indication

Entry in hardcoded exclusion list for directory recursion; indicates intentional avoidance of system folders.

Type

String

Value

Program Files

Referenced By

sub_407fe0 (0x407fe0)

Indication

Exclusion to avoid modifying system/app files; common behavior in ransomware to preserve OS and avoid breaking host.

Type

String

Value

$Recycle.Bin

Referenced By

sub_407fe0 (0x407fe0)

Indication

Excluded folder; suggests careful selection of targets to avoid obvious recovery artifacts.

Type

Constant

Value

0x29A

Referenced By

sub_408c50 (0x408c50)

Indication

Used as a control code when posting tasks to the worker pool; may be a task type.

Type

Constant

Value

0xFFFFFFFF

Referenced By

sub_408ca0 (0x408ca0)

Indication

Used as sentinel/status in task structure created for worker pool.

Type

Data Constant

Value

data_4099d0 (128-bit key used for XOR)

Referenced By

sub_401000 (0x401000), sub_402bf0 (0x402bf0)

Indication

128-bit key used for repeated XOR block-based deobfuscation.

Type

API pattern

Value

GetModuleHandleA / LoadLibraryA / GetProcAddress

Referenced By

sub_4010e0 (0x4010e0)

Indication

Runtime API resolution via decoded strings; hides imports.

Type

Resource IDs

Value

RCDATA resources 0x68 and 0x69

Referenced By

_start (0x402610)

Indication

Embedded configuration or payload stored in resources; one is decoded and compared to "null".

Delphos Labs may make errors. Manual verification is recommended.