// Copyright 2011 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// This proto represents a machine learning model which is used to compute
// the probability that a particular page visited by Chrome is phishing.
//
// Note: sine the machine learning model is trained on the server-side and then
// downloaded onto the client it is important that this proto file stays in
// sync with the server-side copy. Otherwise, the client may not be able to
// parse the server generated model anymore. If you want to change this
// protocol definition or you have questions regarding its format please contact
// [email protected].
syntax = "proto2";
option optimize_for = LITE_RUNTIME;
package safe_browsing;
// This protocol buffer represents a machine learning model that is used in
// client-side phishing detection (in Chrome). The client extracts a set
// of features from every website the user visits. Extracted features map
// feature names to floating point values (e.g., PageSecureLinksFreq -> 0.9).
//
// To compute the phishing score (i.e., the probability that the website is
// phishing) a scorer will simply compute the sum of all rule scores for a
// given set of extracted features. The score of a particular rule corresponds
// to the product of all feature values that are part of the rule times the
// rule weight. If a feature has no value (i.e., is not part of the extracted
// features) its value will be set to zero. The overall score is computed
// by summing up all the rule scores. This overall score is a logodds and can
// be converted to a probability like this:
// p = exp(logodds) / (exp(logodds) + 1).
//
// To make it harder for phishers to reverse engineer our machine learning model
// all the features in the model are hashed with a sha256 hash function. The
// feature extractors also hash the extracted features before scoring happens.
message ClientSideModel {
// In order to save some space we store all the hashed strings in a
// single repeated field and then the rules as well as page terms
// and page words refer to an index in that repeated field. All
// hashes are sha256 hashes stored in binary format.
repeated bytes hashes = 1;
message Rule {
// List of indexes into hashes above which are basically hashed
// features that form the current rule.
repeated int32 feature = 1;
// The weight for this particular rule.
required float weight = 2;
}
// List of rules which make up the model
repeated Rule rule = 2;
// List of indexes that point to the hashed page terms that appear in
// the model. The hashes are computed over page terms that are encoded
// as lowercase UTF-8 strings.
repeated int32 page_term = 3;
// List of hashed page words. The page words correspond to all words that
// appear in page terms. If the term "one two" is in the list of page terms
// then "one" and "two" will be in the list of page words. For page words
// we don't use SHA256 because it is too expensive. We use MurmurHash3
// instead. See: http://code.google.com/p/smhasher.
repeated fixed32 page_word = 4;
// Page terms in page_term contain at most this many page words.
required int32 max_words_per_term = 5;
optional int32 dom_model_version = 18;
// The overall client model version number. Every model update should have a
// different version number and it should always be larger than the previous
// model version.
optional int32 version = 6;
// List of known bad IP subnets.
message IPSubnet {
// The subnet prefix is a valid 16-byte IPv6 address (in network order) that
// is hashed using sha256.
required bytes prefix = 1;
// Network prefix size in bits. Default is an exact-host match.
optional int32 size = 2 [default = 128];
};
repeated IPSubnet bad_subnet = 7;
// Murmur hash seed that was used to hash the page words.
optional fixed32 murmur_hash_seed = 8;
// Maximum number of unique shingle hashes per page.
optional int32 max_shingles_per_page = 9 [default = 200];
// The number of words in a shingle.
optional int32 shingle_size = 10 [default = 4];
// The threshold probability that causes this model to send a ping.
optional float threshold_probability = 11 [default = 0.5];
// Reserved tag numbers holding deprecated fields.
reserved 12;
reserved 13;
reserved 14;
reserved 15;
reserved 16;
optional TfLiteModelMetadata tflite_metadata = 17;
optional TfLiteModelMetadata img_embedding_metadata = 19;
// next available tag number: 20
}
message TfLiteModelMetadata {
// The version number of the visual TFLite model.
optional int32 model_version = 1;
message Threshold {
// The label for the category
optional string label = 1;
// The threshold value
optional float threshold = 2;
// The threshold value for ESB users
optional float esb_threshold = 3;
}
// The list of threshold values for each category in the TFLite model. Pages
// where the model score exceeds one of these thresholds will be sent to
// Safe Browsing for a more definitive classification.
repeated Threshold thresholds = 2;
// The width and height of the input tensor to the corresponding TFLite model.
optional int32 input_width = 3;
optional int32 input_height = 4;
}
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