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[ "]", "today", "www", "[", "." ]
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[ "]", "today", "shop", "[", "." ]
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[ "]", "today", "svc", "[", "." ]
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[ "]", "today", "admin", "[", ".databit", "[", ".today", "cendata", "[", "." ]
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[ "]", "today", "svcws", "[", "." ]
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[ "]", "cendata", "[", "." ]
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[ "]", "today", "PHA", "Family", "Highlights", ":", "Zen", "and", "its", "cousins", "January", "11", ",", "2019", "Google", "Play", "Protect", "detects", "Potentially", "Harmful", "Applications", "(", "PHAs", ")", "which", "Google", "Play", "Protect", "defines", "as", "any", "mobile", "app", "that", "poses", "a", "potential", "security", "risk", "to", "users", "or", "to", "user", "data—commonly", "referred", "to", "as", "\"", "malware", "." ]
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[ "''", "in", "a", "variety", "of", "ways", ",", "such", "as", "static", "analysis", ",", "dynamic", "analysis", ",", "and", "machine", "learning", "." ]
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2121
[ "While", "our", "systems", "are", "great", "at", "automatically", "detecting", "and", "protecting", "against", "PHAs", ",", "we", "believe", "the", "best", "security", "comes", "from", "the", "combination", "of", "automated", "scanning", "and", "skilled", "human", "review", "." ]
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2122
[ "With", "this", "blog", "series", "we", "will", "be", "sharing", "our", "research", "analysis", "with", "the", "research", "and", "broader", "security", "community", ",", "starting", "with", "the", "PHA", "family", ",", "Zen", "." ]
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2123
[ "Zen", "uses", "root", "permissions", "on", "a", "device", "to", "automatically", "enable", "a", "service", "that", "creates", "fake", "Google", "accounts", "." ]
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2124
[ "These", "accounts", "are", "created", "by", "abusing", "accessibility", "services", "." ]
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2125
[ "Zen", "apps", "gain", "access", "to", "root", "permissions", "from", "a", "rooting", "trojan", "in", "its", "infection", "chain", "." ]
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2126
[ "In", "this", "blog", "post", ",", "we", "do", "not", "differentiate", "between", "the", "rooting", "component", "and", "the", "component", "that", "abuses", "root", ":", "we", "refer", "to", "them", "interchangeably", "as", "Zen", "." ]
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2127
[ "We", "also", "describe", "apps", "that", "we", "think", "are", "coming", "from", "the", "same", "author", "or", "a", "group", "of", "authors", "." ]
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2128
[ "All", "of", "the", "PHAs", "that", "are", "mentioned", "in", "this", "blog", "post", "were", "detected", "and", "removed", "by", "Google", "Play", "Protect", "." ]
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2129
[ "Background", "Uncovering", "PHAs", "takes", "a", "lot", "of", "detective", "work", "and", "unraveling", "the", "mystery", "of", "how", "they", "'re", "possibly", "connected", "to", "other", "apps", "takes", "even", "more", "." ]
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2130
[ "PHA", "authors", "usually", "try", "to", "hide", "their", "tracks", ",", "so", "attribution", "is", "difficult", "." ]
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2131
[ "Sometimes", ",", "we", "can", "attribute", "different", "apps", "to", "the", "same", "author", "based", "on", "a", "small", ",", "unique", "pieces", "of", "evidence", "that", "suggest", "similarity", ",", "such", "as", "a", "repetition", "of", "an", "exceptionally", "rare", "code", "snippet", ",", "asset", ",", "or", "a", "particular", "string", "in", "the", "debug", "logs", "." ]
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2132
[ "Every", "once", "in", "a", "while", ",", "authors", "leave", "behind", "a", "trace", "that", "allows", "us", "to", "attribute", "not", "only", "similar", "apps", ",", "but", "also", "multiple", "different", "PHA", "families", "to", "the", "same", "group", "or", "person", "." ]
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2133
[ "However", ",", "the", "actual", "timeline", "of", "the", "creation", "of", "different", "variants", "is", "unclear", "." ]
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2134
[ "In", "April", "2013", ",", "we", "saw", "the", "first", "sample", ",", "which", "made", "heavy", "use", "of", "dynamic", "code", "loading", "(", "i.e.", ",", "fetching", "executable", "code", "from", "remote", "sources", "after", "the", "initial", "app", "is", "installed", ")", "." ]
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2135
[ "Dynamic", "code", "loading", "makes", "it", "impossible", "to", "state", "what", "kind", "of", "PHA", "it", "was", "." ]
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2136
[ "This", "sample", "displayed", "ads", "from", "various", "sources", "." ]
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2137
[ "More", "recent", "variants", "blend", "rooting", "capabilities", "and", "click", "fraud", "." ]
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2138
[ "As", "rooting", "exploits", "on", "Android", "become", "less", "prevalent", "and", "lucrative", ",", "PHA", "authors", "adapt", "their", "abuse", "or", "monetization", "strategy", "to", "focus", "on", "tactics", "like", "click", "fraud", "." ]
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2139
[ "This", "post", "does", "n't", "follow", "the", "chronological", "evolution", "of", "Zen", ",", "but", "instead", "covers", "relevant", "samples", "from", "least", "to", "most", "complex", "." ]
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2140
[ "Apps", "with", "a", "custom-made", "advertisement", "SDK", "The", "simplest", "PHA", "from", "the", "author", "'s", "portfolio", "used", "a", "specially", "crafted", "advertisement", "SDK", "to", "create", "a", "proxy", "for", "all", "ads-related", "network", "traffic", "." ]
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2141
[ "By", "proxying", "all", "requests", "through", "a", "custom", "server", ",", "the", "real", "source", "of", "ads", "is", "opaque", "." ]
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2142
[ "This", "example", "shows", "one", "possible", "implementation", "of", "this", "technique", "." ]
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2143
[ "This", "approach", "allows", "the", "authors", "to", "combine", "ads", "from", "third-party", "advertising", "networks", "with", "ads", "they", "created", "for", "their", "own", "apps", "." ]
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2144
[ "It", "may", "even", "allow", "them", "to", "sell", "ad", "space", "directly", "to", "application", "developers", "." ]
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2145
[ "The", "advertisement", "SDK", "also", "collects", "statistics", "about", "clicks", "and", "impressions", "to", "make", "it", "easier", "to", "track", "revenue", "." ]
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2146
[ "Selling", "the", "ad", "traffic", "directly", "or", "displaying", "ads", "from", "other", "sources", "in", "a", "very", "large", "volume", "can", "provide", "direct", "profit", "to", "the", "app", "author", "from", "the", "advertisers", "." ]
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2147
[ "We", "have", "seen", "two", "types", "of", "apps", "that", "use", "this", "custom-made", "SDK", "." ]
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2148
[ "The", "first", "are", "games", "of", "very", "low", "quality", "that", "mimic", "the", "experience", "of", "popular", "mobile", "games", "." ]
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2149
[ "While", "the", "counterfeit", "games", "claim", "to", "provide", "similar", "functionality", "to", "the", "popular", "apps", ",", "they", "are", "simply", "used", "to", "display", "ads", "through", "a", "custom", "advertisement", "SDK", "." ]
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2150
[ "The", "second", "type", "of", "apps", "reveals", "an", "evolution", "in", "the", "author", "'s", "tactics", "." ]
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2151
[ "Instead", "of", "implementing", "very", "basic", "gameplay", ",", "the", "authors", "pirated", "and", "repackaged", "the", "original", "game", "in", "their", "app", "and", "bundled", "with", "it", "their", "advertisement", "SDK", "." ]
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2152
[ "The", "only", "noticeable", "difference", "is", "the", "game", "has", "more", "ads", ",", "including", "ads", "on", "the", "very", "first", "screen", "." ]
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2153
[ "In", "all", "cases", ",", "the", "ads", "are", "used", "to", "convince", "users", "to", "install", "other", "apps", "from", "different", "developer", "accounts", ",", "but", "written", "by", "the", "same", "group", "." ]
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2154
[ "Those", "apps", "use", "the", "same", "techniques", "to", "monetize", "their", "actions", "." ]
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2155
[ "Click", "fraud", "apps", "The", "authors", "'", "tactics", "evolved", "from", "advertisement", "spam", "to", "real", "PHA", "(", "Click", "Fraud", ")", "." ]
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2156
[ "Click", "fraud", "PHAs", "simulate", "user", "clicks", "on", "ads", "instead", "of", "simply", "displaying", "ads", "and", "waiting", "for", "users", "to", "click", "them", "." ]
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2157
[ "This", "allows", "the", "PHA", "authors", "to", "monetize", "their", "apps", "more", "effectively", "than", "through", "regular", "advertising", "." ]
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2158
[ "This", "behavior", "negatively", "impacts", "advertisement", "networks", "and", "their", "clients", "because", "advertising", "budget", "is", "spent", "without", "acquiring", "real", "customers", ",", "and", "impacts", "user", "experience", "by", "consuming", "their", "data", "plan", "resources", "." ]
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2159
[ "The", "click", "fraud", "PHA", "requests", "a", "URL", "to", "the", "advertising", "network", "directly", "instead", "of", "proxying", "it", "through", "an", "additional", "SDK", "." ]
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2160
[ "The", "command", "&", "control", "server", "(", "C", "&", "C", "server", ")", "returns", "the", "URL", "to", "click", "along", "with", "a", "very", "long", "list", "of", "additional", "parameters", "in", "JSON", "format", "." ]
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2161
[ "After", "rendering", "the", "ad", "on", "the", "screen", ",", "the", "app", "tries", "to", "identify", "the", "part", "of", "the", "advertisement", "website", "to", "click", "." ]
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2162
[ "If", "that", "part", "is", "found", ",", "the", "app", "loads", "Javascript", "snippets", "from", "the", "JSON", "parameters", "to", "click", "a", "button", "or", "other", "HTML", "element", ",", "simulating", "a", "real", "user", "click", "." ]
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2163
[ "Because", "a", "user", "interacting", "with", "an", "ad", "often", "leads", "to", "a", "higher", "chance", "of", "the", "user", "purchasing", "something", ",", "ad", "networks", "often", "\"", "pay", "per", "click", "''", "to", "developers", "who", "host", "their", "ads", "." ]
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2164
[ "Therefore", ",", "by", "simulating", "fraudulent", "clicks", ",", "these", "developers", "are", "making", "money", "without", "requiring", "a", "user", "to", "click", "on", "an", "advertisement", "." ]
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2165
[ "This", "example", "code", "shows", "a", "JSON", "reply", "returned", "by", "the", "C", "&", "C", "server", "." ]
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2166
[ "It", "has", "been", "shortened", "for", "brevity", "." ]
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2167
[ "Based", "on", "this", "JSON", "reply", ",", "the", "app", "looks", "for", "an", "HTML", "snippet", "that", "corresponds", "to", "the", "active", "element", "(", "show_hide", "btnnext", ")", "and", ",", "if", "found", ",", "the", "Javascript", "snippet", "tries", "to", "perform", "a", "click", "(", ")", "method", "on", "it", "." ]
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2168
[ "Rooting", "trojans", "The", "Zen", "authors", "have", "also", "created", "a", "rooting", "trojan", "." ]
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2169
[ "Using", "a", "publicly", "available", "rooting", "framework", ",", "the", "PHA", "attempts", "to", "root", "devices", "and", "gain", "persistence", "on", "them", "by", "reinstalling", "itself", "on", "the", "system", "partition", "of", "rooted", "device", "." ]
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2170
[ "Installing", "apps", "on", "the", "system", "partition", "makes", "it", "harder", "for", "the", "user", "to", "remove", "the", "app", "." ]
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2171
[ "This", "technique", "only", "works", "for", "unpatched", "devices", "running", "Android", "4.3", "or", "lower", "." ]
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2172
[ "Devices", "running", "Android", "4.4", "and", "higher", "are", "protected", "by", "Verified", "Boot", "." ]
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2173
[ "Zen", "'s", "rooting", "trojan", "apps", "target", "a", "specific", "device", "model", "with", "a", "very", "specific", "system", "image", "." ]
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2174
[ "After", "achieving", "root", "access", "the", "app", "tries", "to", "replace", "the", "framework.jar", "file", "on", "the", "system", "partition", "." ]
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2175
[ "Replicating", "framework.jar", "allows", "the", "app", "to", "intercept", "and", "modify", "the", "behavior", "of", "the", "Android", "standard", "API", "." ]
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2176
[ "In", "particular", ",", "these", "apps", "try", "to", "add", "an", "additional", "method", "called", "statistics", "(", ")", "into", "the", "Activity", "class", "." ]
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2177
[ "When", "inserted", ",", "this", "method", "runs", "every", "time", "any", "Activity", "object", "in", "any", "Android", "app", "is", "created", "." ]
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2178
[ "This", "happens", "all", "the", "time", "in", "regular", "Android", "apps", ",", "as", "Activity", "is", "one", "of", "the", "fundamental", "Android", "UI", "elements", "." ]
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2179
[ "The", "only", "purpose", "of", "this", "method", "is", "to", "connect", "to", "the", "C", "&", "C", "server", "." ]
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2180
[ "The", "Zen", "trojan", "After", "achieving", "persistence", ",", "the", "trojan", "downloads", "additional", "payloads", ",", "including", "another", "trojan", "called", "Zen", "." ]
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2181
[ "Zen", "requires", "root", "to", "work", "correctly", "on", "the", "Android", "operating", "system", "." ]
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2182
[ "The", "Zen", "trojan", "uses", "its", "root", "privileges", "to", "turn", "on", "accessibility", "service", "(", "a", "service", "used", "to", "allow", "Android", "users", "with", "disabilities", "to", "use", "their", "devices", ")", "for", "itself", "by", "writing", "to", "a", "system-wide", "setting", "value", "enabled_accessibility_services", "." ]
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2183
[ "Zen", "does", "n't", "even", "check", "for", "the", "root", "privilege", ":", "it", "just", "assumes", "it", "has", "it", "." ]
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2184
[ "This", "leads", "us", "to", "believe", "that", "Zen", "is", "just", "part", "of", "a", "larger", "infection", "chain", "." ]
[ 10, 10, 10, 10, 10, 10, 1, 10, 10, 10, 10, 10, 10, 10, 10, 10 ]
2185
[ "The", "trojan", "implements", "three", "accessibility", "services", "directed", "at", "different", "Android", "API", "levels", "and", "uses", "these", "accessibility", "services", ",", "chosen", "by", "checking", "the", "operating", "system", "version", ",", "to", "create", "new", "Google", "accounts", "." ]
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2186
[ "This", "is", "done", "by", "opening", "the", "Google", "account", "creation", "process", "and", "parsing", "the", "current", "view", "." ]
[ 10, 10, 10, 10, 10, 10, 2, 10, 10, 10, 10, 10, 10, 10, 10, 10 ]
2187
[ "The", "app", "then", "clicks", "the", "appropriate", "buttons", ",", "scrollbars", ",", "and", "other", "UI", "elements", "to", "go", "through", "account", "sign-up", "without", "user", "intervention", "." ]
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2188
[ "During", "the", "account", "sign-up", "process", ",", "Google", "may", "flag", "the", "account", "creation", "attempt", "as", "suspicious", "and", "prompt", "the", "app", "to", "solve", "a", "CAPTCHA", "." ]
[ 10, 10, 10, 10, 10, 10, 2, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10 ]
2189
[ "To", "get", "around", "this", ",", "the", "app", "then", "uses", "its", "root", "privilege", "to", "inject", "code", "into", "the", "Setup", "Wizard", ",", "extract", "the", "CAPTCHA", "image", ",", "and", "sends", "it", "to", "a", "remote", "server", "to", "try", "to", "solve", "the", "CAPTCHA", "." ]
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2190
[ "It", "is", "unclear", "if", "the", "remote", "server", "is", "capable", "of", "solving", "the", "CAPTCHA", "image", "automatically", "or", "if", "this", "is", "done", "manually", "by", "a", "human", "in", "the", "background", "." ]
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2191
[ "After", "the", "server", "returns", "the", "solution", ",", "the", "app", "enters", "it", "into", "the", "appropriate", "text", "field", "to", "complete", "the", "CAPTCHA", "challenge", "." ]
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2192
[ "The", "Zen", "trojan", "does", "not", "implement", "any", "kind", "of", "obfuscation", "except", "for", "one", "string", "that", "is", "encoded", "using", "Base64", "encoding", "." ]
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2193
[ "It", "'s", "one", "of", "the", "strings", "-", "\"", "How", "you", "'ll", "sign", "in", "''", "-", "that", "it", "looks", "for", "during", "the", "account", "creation", "process", "." ]
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2194
[ "The", "code", "snippet", "below", "shows", "part", "of", "the", "screen", "parsing", "process", "." ]
[ 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10 ]
2195
[ "Apart", "from", "injecting", "code", "to", "read", "the", "CAPTCHA", ",", "the", "app", "also", "injects", "its", "own", "code", "into", "the", "system_server", "process", ",", "which", "requires", "root", "privileges", "." ]
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2196
[ "This", "indicates", "that", "the", "app", "tries", "to", "hide", "itself", "from", "any", "anti-PHA", "systems", "that", "look", "for", "a", "specific", "app", "process", "name", "or", "does", "not", "have", "the", "ability", "to", "scan", "the", "memory", "of", "the", "system_server", "process", "." ]
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2197
[ "The", "app", "also", "creates", "hooks", "to", "prevent", "the", "phone", "from", "rebooting", ",", "going", "to", "sleep", "or", "allowing", "the", "user", "from", "pressing", "hardware", "buttons", "during", "the", "account", "creation", "process", "." ]
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2198
[ "These", "hooks", "are", "created", "using", "the", "root", "access", "and", "a", "custom", "native", "code", "called", "Lmt_INJECT", ",", "although", "the", "algorithm", "for", "this", "is", "well", "known", "." ]
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2199
[ "First", ",", "the", "app", "has", "to", "turn", "off", "SELinux", "protection", "." ]
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