Potentially unwanted program that changes the startpage of browsers to induce ad impressions.
rule win_startpage_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2022-08-05" version = "1" description = "Detects win.startpage." info = "autogenerated rule brought to you by yara-signator" tool = "yara-signator v0.6.0" signator_config = "callsandjumps;datarefs;binvalue" malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.startpage" malpedia_rule_date = "20220805" malpedia_hash = "6ec06c64bcfdbeda64eff021c766b4ce34542b71" malpedia_version = "20220808" malpedia_license = "CC BY-SA 4.0" malpedia_sharing = "TLP:WHITE" /* DISCLAIMER * The strings used in this rule have been automatically selected from the * disassembly of memory dumps and unpacked files, using YARA-Signator. * The code and documentation is published here: * https://github.com/fxb-cocacoding/yara-signator * As Malpedia is used as data source, please note that for a given * number of families, only single samples are documented. * This likely impacts the degree of generalization these rules will offer. * Take the described generation method also into consideration when you * apply the rules in your use cases and assign them confidence levels. */ strings: $sequence_0 = { 8955fc 8b32 85f6 0f84ba000000 53 57 8b7a04 } // n = 7, score = 200 // 8955fc | mov dword ptr [ebp - 4], edx // 8b32 | mov esi, dword ptr [edx] // 85f6 | test esi, esi // 0f84ba000000 | je 0xc0 // 53 | push ebx // 57 | push edi // 8b7a04 | mov edi, dword ptr [edx + 4] $sequence_1 = { c20800 6a00 b8???????? e8???????? 8bf1 8b5508 85d2 } // n = 7, score = 200 // c20800 | ret 8 // 6a00 | push 0 // b8???????? | // e8???????? | // 8bf1 | mov esi, ecx // 8b5508 | mov edx, dword ptr [ebp + 8] // 85d2 | test edx, edx $sequence_2 = { 53 8bcf e8???????? 53 ba???????? 895df0 8d4dec } // n = 7, score = 200 // 53 | push ebx // 8bcf | mov ecx, edi // e8???????? | // 53 | push ebx // ba???????? | // 895df0 | mov dword ptr [ebp - 0x10], ebx // 8d4dec | lea ecx, [ebp - 0x14] $sequence_3 = { ff37 8b35???????? ff75fc 53 50 ff750c } // n = 6, score = 200 // ff37 | push dword ptr [edi] // 8b35???????? | // ff75fc | push dword ptr [ebp - 4] // 53 | push ebx // 50 | push eax // ff750c | push dword ptr [ebp + 0xc] $sequence_4 = { 0f8578010000 8d8d80feffff e8???????? 8d8d80feffff e8???????? 84c0 0f845a010000 } // n = 7, score = 200 // 0f8578010000 | jne 0x17e // 8d8d80feffff | lea ecx, [ebp - 0x180] // e8???????? | // 8d8d80feffff | lea ecx, [ebp - 0x180] // e8???????? | // 84c0 | test al, al // 0f845a010000 | je 0x160 $sequence_5 = { 68ec010000 b8???????? e8???????? 8bd9 6a00 ff15???????? 85c0 } // n = 7, score = 200 // 68ec010000 | push 0x1ec // b8???????? | // e8???????? | // 8bd9 | mov ebx, ecx // 6a00 | push 0 // ff15???????? | // 85c0 | test eax, eax $sequence_6 = { 7549 895df0 895dfc 8b07 ff5010 8d55f0 52 } // n = 7, score = 200 // 7549 | jne 0x4b // 895df0 | mov dword ptr [ebp - 0x10], ebx // 895dfc | mov dword ptr [ebp - 4], ebx // 8b07 | mov eax, dword ptr [edi] // ff5010 | call dword ptr [eax + 0x10] // 8d55f0 | lea edx, [ebp - 0x10] // 52 | push edx $sequence_7 = { ff15???????? 8907 663918 7419 8a55af 8a45ad } // n = 6, score = 200 // ff15???????? | // 8907 | mov dword ptr [edi], eax // 663918 | cmp word ptr [eax], bx // 7419 | je 0x1b // 8a55af | mov dl, byte ptr [ebp - 0x51] // 8a45ad | mov al, byte ptr [ebp - 0x53] $sequence_8 = { ff30 ff75ec e8???????? c645fc01 8b4d08 8d49f0 e8???????? } // n = 7, score = 200 // ff30 | push dword ptr [eax] // ff75ec | push dword ptr [ebp - 0x14] // e8???????? | // c645fc01 | mov byte ptr [ebp - 4], 1 // 8b4d08 | mov ecx, dword ptr [ebp + 8] // 8d49f0 | lea ecx, [ecx - 0x10] // e8???????? | $sequence_9 = { 33c0 40 6a7d 59 66390f 0f85a4faffff eb18 } // n = 7, score = 200 // 33c0 | xor eax, eax // 40 | inc eax // 6a7d | push 0x7d // 59 | pop ecx // 66390f | cmp word ptr [edi], cx // 0f85a4faffff | jne 0xfffffaaa // eb18 | jmp 0x1a condition: 7 of them and filesize < 2277376 }
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